World Trade Center (1973–2001)



'Note: This article is about the original World Trade Center complex which was destroyed in the September 11 attacks. For the rebuilt World Trade Center complex, see- World Trade Center (2001–present).'

'For the main building of the rebuilt complex, see One World Trade Center. For other uses, see World Trade Center (disambiguation).'

Over view
The World Trade Center was a large complex of seven buildings in Lower Manhattan, New York City, United States. It was a major twin office block unit owned by the Port Authority of New York and New Jersey that was erected in 1973 in Manhattan's financial district. It was a key fixture of the district for 37 years until it was destroyed by the terrorist attacks of 9\11. It featured landmark twin towers, which opened on April 4, 1973, and were destroyed in the September 11 attacks, with 7 World Trade Center collapsing later that day due to the damage it suffered when the twin towers collapsed that morning. The other buildings in the complex were severely damaged by the collapse of the twin towers, and their ruins were eventually demolished.

At the time of their completion, the "Twin Towers" — the original 1 World Trade Center, at 1,368 feet (417 m); and 2 World Trade Center, at 1,362 feet (415 m) — were the tallest buildings in the world. The other buildings in the complex included the Marriott World Trade Center (3 WTC), 4 WTC, 5 WTC, 6 WTC, and 7 WTC. All these buildings were built between 1975 and 1985, with a construction cost of $400 million ($2,300,000,000 in 2014 dollars). The complex was located in New York City's Financial District and contained 13,400,000 square feet (1,240,000 m2) of office space.

The World Trade Center experienced a fire on February 13, 1975, a bombing on February 26, 1993, and a robbery on January 14, 1998. In 1998, the Port Authority decided to privatize the World Trade Center, leasing the buildings to a private company to manage, and awarded the lease to Silverstein Properties in July 2001.

On the morning of September 11, 2001, fanatical Al-Qaeda affiliated hijackers flew two Boeing 767 jets into the complex, beginning with the North Tower at 8:46 a.m., then the South Tower at 9:03 a.m., in a coordinated act of terrorism. After burning for 56 minutes, the South Tower collapsed at 9:59 a.m. 29 minutes later, at 10:28 a.m. (102 minutes after being struck by the plane), the North Tower collapsed. The attacks on the World Trade Center killed 2,606 people in and within the vicinity of the towers, as well as all 157 on board the two aircraft.

Falling debris from the towers, combined with fires that the debris initiated in several surrounding buildings, led to the partial or complete collapse of all the other buildings in the complex and caused catastrophic damage to ten other large structures in the surrounding area, including the World Financial Center and Deutsche Bank Building; three buildings in the World Trade Center complex collapsed due to fire-induced structural failure, and when the North Tower collapsed, debris fell on the nearby 7 WTC, damaging it and starting fires so that it eventually collapsed. The process of cleaning up and recovery at the World Trade Center site took eight months.

The World Trade Center complex was rebuilt over a span of more than a decade. The site is being rebuilt with six new skyscrapers, while a memorial to those killed in the attacks and a new rapid transit hub have both opened. One World Trade Center, the tallest building in the United States, is the lead building for the defiant new complex, reaching more than 100 stories upon its completion in November 2014.

Stats



 * name = World Trade Centre.
 * location = Lower Manhattan, New York City.
 * status = Destroyed by terrorists on 9\11\2001 and replaced by the One World Trade Center in 2014.
 * Planned out=
 * Groundbreaking = 1966.
 * start_date =  .
 * completion_date = 1973.
 * opening =  1973.
 * renovation_date = 1979, 1983  and 1993-1994.
 * building_type = Twin towered office block.
 * architectural_style= Modernist.
 * antenna_spire = A tall communication mast one and no communications mast on the other.
 * roof level height =
 * floor_count =  110 in both.
 * elevator_count = 1 and 2 WTC: 99 each.
 * Unit cost =
 * Floor_area =
 * architect =  Minoru Yamasaki and Emery Roth & Sons.
 * structural_engineer=Worthington, Skilling, Helle & Jackson and Leslie E. Robertson Associates.
 * main_contractor = N\A.
 * developer = N\A.
 * owner = Port Authority of New York and New Jersey.
 * Facility management = Port Authority of New York and New Jersey until 2001, then Vornado .

The topping out ceremony of 1 WTC (North Tower) took place on, December 23, 1970,, while 2 WTC's ceremony (South Tower) occurred later on July 19, 1971.

The whole complex of buildings accommodated 50,000 workers and 200,000 daily visitors in 10 million square feet of space. The unit cost was $400 million ($2,300,000,000 in 2014 dollars) for the whole centre.

Local Geology
The western portion of the World Trade Center site was originally under the Hudson River, with the shoreline in the vicinity of Greenwich Street. It was on this shoreline close to the intersection of Greenwich and the former Dey Street that Dutch explorer Adriaen Block's ship, the Tyger, burned to the waterline in November 1613, stranding Block and his crew and forcing them to overwinter on the island. They built the first European settlement in Manhattan. The remains of the ship were buried under landfill when the shoreline was extended starting in 1797, and were discovered during excavation work in 1916. The remains of a second ship from the eighteenth century were discovered in 2010 during excavation work at the site. The ship, believed to be a Hudson River sloop, was found just south of where the Twin Towers used to stand, about 20 feet below the surface.

Before the World Trade Center


Later, the area became Radio Row. New York City's Radio Row, which existed from 1921 to 1966, was a warehouse district on the Lower West Side in the Financial District. Harry Schneck opened City Radio on Cortlandt Street in 1921, and eventually the area held several blocks of electronics stores, with Cortlandt Street as its central axis. The used radios, war surplus electronics (e.g., ARC-5 radios), junk, and parts often piled so high they would spill out onto the street, attracting collectors and scroungers. According to a business writer, it also was the origin of the electronic component distribution business.

The idea of establishing a World Trade Center in New York City was first proposed in 1943. The New York State Legislature passed a bill authorizing New York Governor Thomas E. Dewey to begin developing plans for the project but the plans were put on hold in 1949. During the late 1940s and 1950s, economic growth in New York City was concentrated in Midtown Manhattan. To help stimulate urban renewal in Lower Manhattan, David Rockefeller suggested that the Port Authority build a World Trade Center in Lower Manhattan.

Plans for the use of eminent domain to remove the shops in Radio Row bounded by Vesey, Church, Liberty, and West Streets began in 1961 when the Port Authority of New York and New Jersey was deciding to build the world's first world trade center. They had two choices: the east side of Lower Manhattan, near the South Street Seaport; and the west side, near the H&M station, Hudson Terminal. Initial plans, made public in 1961, identified a site along the East River for the World Trade Center. As a bi-state agency, the Port Authority required approval for new projects from the governors of both New York and New Jersey. New Jersey Governor Robert B. Meyner objected to New York getting a $335 million project. Toward the end of 1961, negotiations with outgoing New Jersey Governor Meyner reached a stalemate.

At the time, ridership on New Jersey's Hudson and Manhattan Railroad (H&M) had declined substantially from a high of 113 million riders in 1927 to 26 million in 1958 after new automobile tunnels and bridges had opened across the Hudson River. In a December 1961 meeting between Port Authority director Austin J. Tobin and newly elected New Jersey Governor Richard J. Hughes, the Port Authority offered to take over the Hudson & Manhattan Railroad to have it become the Port Authority Trans-Hudson (PATH). The Port Authority also decided to move the World Trade Center project to the Hudson Terminal building site on the west side of Lower Manhattan, a more convenient location for New Jersey commuters arriving via PATH. With the new location and Port Authority acquisition of the H&M Railroad, New Jersey agreed to support the World Trade Center project. In compensation for Radio Row business owners' displacement, the PANYNJ gave each business $3,000 each, without regard to how long the business had been there or how prosperous the business was. After the area had been purchased for the World Trade Center in March 1964, Radio Row was demolished starting in March 1965. It was completely demolished by 1966.

Approval was also needed from New York City Mayor John Lindsay and the New York City Council. Disagreements with the city centered on tax issues. On August 3, 1966, an agreement was reached that the Port Authority would make annual payments to the City in lieu of taxes for the portion of the World Trade Center leased to private tenants. In subsequent years, the payments would rise as the real estate tax rate increased.

Planning permissions given
In 1942, Austin J. Tobin became the Executive Director of the Port Authority, beginning a 30-year career during which he oversaw the planning and development of the World Trade Center. The concept of establishing a "world trade center" was conceived during the post–World War II period, when the United States thrived economically and international trade was increasing. In 1946, the New York State Legislature passed a bill that called for a "world trade center" to be established. The World Trade Corporation was founded, and a board was appointed by New York Governor Thomas E. Dewey to develop plans for the project. Architect John Eberson and his son Drew devised a plan that included 21 buildings over a ten-block area, at an estimated cost of $150 million. In 1949, the World Trade Corporation was dissolved by the New York State Legislature, and plans for a "world trade center" were put on hold.

In the beginning
During the post-war period, economic growth was concentrated in Midtown Manhattan, in part stimulated by the Rockefeller Center, which was developed in the 1930s. Meanwhile, Lower Manhattan was left out of the economic boom. One exception was the construction of One Chase Manhattan Plaza in the Financial District by David Rockefeller, who led urban renewal efforts in Lower Manhattan.[5] In 1958, Rockefeller established the Downtown-Lower Manhattan Association (DLMA), which commissioned Skidmore, Owings and Merrill to draw up plans for revitalizing Lower Manhattan. The plans, made public in late June 1960, called for a World Trade Center to be built on a 13-acre (53,000 m2) site along the East River, from Old Slip to Fulton Street and between Water Street and South Street.[6][7] The complex would include a 900-foot (275 m) long exhibition hall, and a 50–70 story building, with some of its upper floors used as a hotel.[8] Other amenities would include a theater, shops, and restaurants.[9] The plan also called for a new securities exchange building, which the Downtown-Lower Manhattan Association hoped would house the New York Stock Exchange.[7]

David Rockefeller suggested that the Port Authority would be a logical choice for taking on the project,[7] and argued that the Trade Center would provide great benefits in facilitating and increasing volume of international commerce coming through the Port of New York.[9] Given the importance of New York City in global commerce, Port Authority director Austin J. Tobin remarked that the proposed project should be the World Trade Center, and not just a "world trade center."[10] After a year-long review of the proposal, the Port Authority formally backed the project on March 11, 1961.[11]

The agreement


Location of World Trade Center (in red) and originally proposed site (in orange) The States of New York and New Jersey also needed to approve the project, given their control and oversight role of the Port Authority. Objections to the plan came from New Jersey Governor Robert B. Meyner, who resented that New York would be getting this $335 million project.[5] Meanwhile, ridership on New Jersey's Hudson and Manhattan Railroad (H&M) had declined substantially from a high of 113 million riders in 1927 to 26 million in 1958, after new automobile tunnels and bridges opened across the Hudson River.[12] Toward the end of 1961, negotiations with outgoing New Jersey Governor Meyner regarding the World Trade Center project reached a stalemate. In December 1961, Tobin met with newly elected New Jersey Governor Richard J. Hughes, and made a proposal to shift the World Trade Center project to a west side site where the Hudson Terminal was located.[13] In acquiring the Hudson & Manhattan Railroad, the Port Authority would also acquire the Hudson Terminal and other buildings which were deemed obsolete.[13] On January 22, 1962, the two states reached an agreement to allow the Port Authority to take over the railroad and to build the World Trade Center on Manhattan's lower west side.[14] The shift in location for the World Trade Center to a site more convenient to New Jersey, together with Port Authority acquisition of the H&M Railroad, brought New Jersey to agreement in support of the World Trade Center project.



Design announced
On September 20, 1962, the Port Authority announced the selection of Minoru Yamasaki as lead architect, and Emery Roth & Sons as associate architects.[30] Originally, Yamasaki submitted to the Port Authority a concept incorporating twin towers, but with each building only 80 stories tall. Yamasaki remarked that the "obvious alternative, a group of several large buildings, would have looked like a housing project."[31] Yamasaki's design for the World Trade Center was unveiled to the public on January 18, 1964, with an eight-foot model.[31] The towers had a square plan, approximately 207 feet (63 m) in dimension on each side.[32] The buildings were designed with narrow office windows, only 18 inches (45 cm) wide, which reflected on Yamasaki's fear of heights and desire to make building occupants feel secure.[33] Yamasaki's design called for the building facades to be sheathed in aluminum-alloy.[34]

To meet the Port Authority's requirement to build 10 million square feet (930,000 m²) of office space, the buildings would each need to be 110 stories tall. A major limiting factor in building heights is elevators; the taller the building, the more elevators are needed to service the building, requiring more space-consuming elevator banks.[35] Yamasaki and the engineers decided to use a new system that included sky lobbies, which are floors where people can switch from a large-capacity express elevator, which goes only to the sky lobbies, to a local elevator that goes to each floor in a section (the local elevators can be stacked within the same elevator shaft). Located on the 44th and 78th floors of each tower, the sky lobbies enabled the elevators to be used efficiently, while also increasing the amount of usable space on each floor from 62 to 75 percent by reducing the number of required elevator shafts.[36] The World Trade Center towers were the second supertall buildings to use sky lobbies, after the John Hancock Center in Chicago.[37] This system was inspired by the New York City Subway system, whose lines include local stations where local trains stop and express stations where all trains stop.[38]

Original architectural and engineering model. This model is now on permanent display at the National September 11th. Memorial and Museum in NYC. Yamasaki, who had previously designed Saudi Arabia's Dhahran International Airport with the Saudi Binladin Group, incorporated features of Arabic architecture into the design of the World Trade Center. The plaza was modelled after Mecca, incorporating features such as a vast delineated square, a fountain, and a radial circular pattern. Yamasaki described the plaza as "a mecca, a great relief from the narrow streets and sidewalks of the Wall Street area."[39] He also incorporated other features of Arabic architecture into the building design, including pointed arches, interweaving tracery of prefabricated concrete, a minaret like flight tower, and arabesque patterns.[40]

The World Trade Center design brought criticism of its aesthetics from the American Institute of Architects and other groups.[34][41] Lewis Mumford, author of The City in History and other works on urban planning, criticized the project and described it and other new skyscrapers as "just glass-and-metal filing cabinets."[42] Television broadcasters raised concerns that the World Trade Center twin towers would cause interference in television reception for viewers in the New York City area.[43] In response to these concerns, the Port Authority offered to provide new television transmission facilities at the World Trade Center.[44] The Linnaean Society of the American Museum of Natural History also opposed the Trade Center project, citing hazards the buildings would impose on migrating birds.[45]

The structural engineering firm Worthington, Skilling, Helle & Jackson worked to implement Yamasaki's design, developing the tube-frame structural system used in the buildings. The Port Authority's Engineering Department served as foundation engineers, Joseph R. Loring & Associates as electrical engineers, and Jaros, Baum & Bolles as mechanical engineers. Tishman Realty & Construction Company was the general contractor on the World Trade Center project. Guy F. Tozzoli, director of the World Trade Department at the Port Authority, and the Port Authority's Chief Engineer, Rino M. Monti, oversaw the project.[46]

Structural design
As an interstate agency, the Port Authority was not subject to local laws and regulations of the City of New York, including building codes. Nonetheless, the Port Authority required architects and structural engineers to follow the New York City building codes. At the time when the World Trade Center was planned, new building codes were being devised to replace the 1938 version that was still in place. The structural engineers ended up following draft versions of the new 1968 building codes, which incorporated "advanced techniques" in building design.

The World Trade Center towers included many structural engineering innovations in skyscraper design and construction, which allowed the buildings to reach new heights and become the tallest in the world. Traditionally, skyscrapers used a skeleton of columns distributed throughout the interior to support building loads, with interior columns disrupting the floor space. The tube-frame concept, earlier introduced by Fazlur Khan, was a major innovation, allowing open floor plans and more space to rent. The buildings used high-strength, load-bearing perimeter steel columns called Vierendeel trusses that were spaced closely together to form a strong, rigid wall structure. There were 60 perimeter columns, narrowly spaced, on each side of the buildings. In all, the perimeter walls of the towers were 210 feet (64 m) on each side, and the corners were beveled. The perimeter columns were designed to provide support for virtually all lateral loads (such as wind loads) and to share the gravity loads with the core columns. Structural analysis of major portions of the World Trade Center were computed on an [https://en.wikipedia.org/wiki/IBM_1620 IBM 1620

Typical WTC architectural floor plan


The perimeter structure was constructed with extensive use of prefabricated modular pieces, which consisted of three columns, three stories tall, connected by spandrel plates. The perimeter columns had a square cross section, 14 inches (36 cm) on a side, and were constructed of welded steel plate.[50]  The thickness of the plates and grade of structural steelvaried over the height of the tower, ranging from 36,000 to 100,000 pounds per square inch[51]  (260 to 670 MPa). The strength of the steel and thickness of the steel plates decreased with height because they were required to support lesser amounts of building mass on higher floors.[50]  The tube-frame design required 40 percent less structural steel than conventional building designs.[52]  From the 7th floor to the ground level, and down to the foundation, the columns were spaced 10 feet (3 m) apart.[53]  All columns were placed on bedrock, which, unlike that in Midtown Manhattan, where the bedrock is shallow, is at 65–85 feet (20–26 m) below the surface.[54]

The spandrel plates were welded to the columns to create the modular pieces off-site at the fabrication shop.[55]  The modular pieces were typically 52 inches (1.3 m) deep, and extended for two full floors and half of two more floors.[50] Adjacent modules were bolted together, with the splices occurring at mid-span of the columns and spandrels. The spandrel plates were located at each floor, transmitting shear stress between columns, allowing them to work together in resisting lateral loads. The joints between modules were staggered vertically, so the column splices between adjacent modules were not at the same floor.[50]

The building's core housed the elevator and utility shafts, restrooms, three stairwells, and other support spaces. The core of each tower was a rectangular area 87 by 135 feet (27 by 41 m), and contained 47 steel columns running from the bedrock to the top of the tower.[50]  The columns tapered after the 66th floor, and consisted of welded box-sections at lower floors and rolled wide-flange sections at upper floors. The structural core in 1 WTC was oriented with the long axis east to west, while that of 2 WTC was oriented north to south. All elevators were located in the core. Each building had three stairwells, also in the core, except on themechanical floors where the two outside stairwells temporarily left the core in order to avoid the express elevator machine rooms, and then rejoined the core by means of a transfer corridor.[56]  It was this arrangement that allowed Stairwell A of 2 WTC to remain passable after the aircraft impact on September 11, 2001.[57]

Composite floor truss system


The large, column-free space between the perimeter and core was bridged by prefabricated floor trusses. The floors supported their own weight, as well as live loads, provided lateral stability to the exterior walls, and distributed wind loads among the exterior walls. The floors consisted of 4-inch (10 cm) thick lightweight concrete slabs laid on a fluted steel deck with shear connections for composite action.<sup class="reference" id="cite_ref-NIST-chapter1_50-5" style="line-height:1;unicode-bidi:isolate;white-space:nowrap;font-size:11.2px;">[50]  A grid of lightweight bridging trusses and main trusses supported the floors. The trusses had a span of 60 feet (18 m) in the long-span areas and 35 feet (11 m) in the short span area.<sup class="reference" id="cite_ref-NIST-chapter1_50-6" style="line-height:1;unicode-bidi:isolate;white-space:nowrap;font-size:11.2px;">[50]  The trusses connected to the perimeter at alternate columns, and were on 6-foot-8-inch (2.03 m) centers. The top chords of the trusses were bolted to seats welded to the spandrels on the exterior side and a channel welded to the core columns on the interior side. The floors were connected to the perimeter spandrel plates with viscoelastic dampers, which helped reduce the amount of sway felt by building occupants.<sup class="reference" id="cite_ref-NIST-chapter1_50-7" style="line-height:1;unicode-bidi:isolate;white-space:nowrap;font-size:11.2px;">[50]

<p style="margin-top:0.5em;margin-bottom:0.5em;line-height:22.4px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">Hat trusses (or "outrigger truss") located from the 107th floor to the top of the buildings were designed to support a tall communication antenna on top of each building.<sup class="reference" id="cite_ref-NIST-chapter1_50-8" style="line-height:1;unicode-bidi:isolate;white-space:nowrap;font-size:11.2px;">[50]  Only 1 WTC (north tower) actually had an antenna fitted, which was added in 1978.<sup class="reference" id="cite_ref-58" style="line-height:1;unicode-bidi:isolate;white-space:nowrap;font-size:11.2px;">[58]  The truss system consisted of six trusses along the long axis of the core and four along the short axis. This truss system allowed some load redistribution between the perimeter and core columns and supported the transmission tower.

Wind effects
The tube frame design using steel core and perimeter columns protected with sprayed-on fire resistant material created a relatively lightweight structure that would sway more in response to the wind, compared to traditional structures such as the Empire State Building that have thick, heavy masonry for fireproofing of steel structural elements During the design process, wind tunnel tests were done at Colorado State University and at the National Physical Laboratory in the United Kingdom to establish design wind pressures that the World Trade Center towers could be subjected to and structural response to those forces. Experiments were also done to evaluate how much sway occupants could tolerate. Subjects were recruited for "free eye exams," while the real purpose of the experiment was to subject them to simulated building sway and find out how much they could comfortably tolerate. Many subjects did not respond well, experiencing dizziness and other ill effects. One of the chief engineers Leslie Robertson worked with Canadian engineer Alan G. Davenport to develop viscoelastic dampers to absorb some of the sway. These viscoelastic dampers, used throughout the structures at the joints between floor trusses and perimeter columns, along with some other structural modifications reduced the building sway to an acceptable level. Wind is always an issue with tall structure.

Aircraft impact
The structural engineers on the project also considered the possibility that an aircraft could crash into the building. In July 1945, a B-25 bomber that was lost in the fog had crashed into the 78th and 79th floors of the Empire State Building. A year later, another airplane nearly crashed into the 40 Wall Street building, and there was another close call at the Empire State Building. In designing the World Trade Center, Leslie Robertson considered the scenario of the impact of a jet airliner, the Boeing 707, which might be lost in the fog, seeking to land at JFK or at Newark airports. The National Institute of Standards and Technology (NIST) found a three-page white paper that mentioned another aircraft impact analysis, involving impact of a jet at 600 mph (970 km/h), was indeed considered, but NIST could not locate the documentary evidence of the aircraft impact analysis.

Fire protection
Sprayed-fire resistant materials (SFRMs) were used to protect some structural steel elements in the towers, including all floor trusses and beams. Gypsum wallboard in combination with SFRMs, or in some cases gypsum wallboard alone, was used to protect core columns. Vermiculite plaster was used on the interior-side and SFRMs on the other three sides of the perimeter columns for fire protection. The 1968 New York City building codes were more lenient in some aspects of fire protection, such as allowing three exit stairwells in the World Trade Center towers, instead of six as required under older building codes.

In April 1970, the New York City Department of Air Resources ordered contractors building the World Trade Center to stop the spraying of asbestos as an insulating material.

More fireproofing was added after a fire in February 1975 that spread to six floors before being extinguished. After the 1993 bombing, inspections found fireproofing to be deficient. The Port Authority was in the process of replacing it, but replacement had been completed on only 18 floors in WTC 1, including all the floors affected by the aircraft impact and fires on September 11, and on 13 floors in WTC 2, although only three of these floors (77, 78, and 85) were directly affected by the aircraft impact.

The 1968 New York City building codes did not require sprinklers for high-rise buildings, except for underground spaces. In accordance with building codes, sprinklers were originally installed only in the underground parking structures of the World Trade Center. Following a major fire in February 1975, the Port Authority decided to start installing sprinklers throughout the buildings. By 1993, nearly all of 2 WTC and 85 percent of 1 WTC had sprinklers installed, and the entire complex was retrofitted by 2001.

Sky Lobbies
A sky lobby is an intermediate interchange floor where people can change from an express elevator that stops only at the sky lobby to a local elevator which stops at every floor within a segment of the building. When designing very tall (supertall) buildings, supplying enough elevators is a problem – travellers wanting to reach a specific higher floor may conceivably have to stop at a very large number of other floors on the way up to let other passengers off and on. This increases travel time, and indirectly requires many more elevator shafts to still allow acceptable travel times – thus reducing effective floor space on each floor for all levels. (The other main technique to increase usage without adding more elevator shafts is double-deck elevators.)

Early uses of the sky lobby include the original Twin Towers of the World Trade Center and the John Hancock Center in Chicago.

Construction


In March 1965, the Port Authority began acquiring property at the World Trade Center site.[30] Demolition work began on March 21, 1966, to clear thirteen square blocks of low rise buildings in Radio Row for construction of the World Trade Center.[31] Groundbreaking for the construction of the World Trade Center took place on August 5, 1966.[54] The Ajax Wrecking and Lumber Corporation was hired for the demolition work, which began on March 21, 1966 to clear the site for construction of the World Trade Center.

The site of the World Trade Center was located on landfill with the bedrock located 65 feet (20 m) below.[55] To construct the World Trade Center, it was necessary to build a "bathtub" with a slurry wall around the West Street side of the site, to keep water from the Hudson River out.[56] The slurry method selected by Port Authority's chief engineer, John M. Kyle, Jr., involved digging a trench, and as excavation proceeded, filling the space with a "slurry" mixture composed of bentonite and water, which plugged holes and kept groundwater out. When the trench was dug out, a steel cage was inserted and concrete was poured in, forcing the "slurry" out. It took fourteen months for the slurry wall to be completed. It was necessary before excavation of material from the interior of the site could begin.[57] The 1,200,000 cubic yards (920,000 m3) of material excavated were used (along with other fill and dredge material) to expand the Manhattan shoreline across West Street to form Battery Park City.[58][59]

In January 1967, the Port Authority awarded $74 million in contracts to various steel suppliers, and Karl Koch was hired to erect the steel.[60] Tishman Realty & Construction was hired in February 1967 to oversee construction of the project.[61] Construction work began on the North Tower in August 1968; construction on the South Tower was underway by January 1969.[62] The original Hudson Tubes, carrying PATH trains into Hudson Terminal, remained in service as elevated tunnels during the construction process until 1971 when a new PATH station opened.[63]

The topping out ceremony of 1 WTC (North Tower) took place on December 23, 1970, while 2 WTC's ceremony (South Tower) occurred later on July 19, 1971.[62] The first tenants moved into the North Tower on December 15, 1970;[64] the South Tower accepted tenants in January 1972.[65] When the World Trade Center twin towers were completed, the total costs to the Port Authority had reached $900 million.[66] The ribbon cutting ceremony was on April 4, 1973.[67]

In addition to the twin towers, the plan for the World Trade Center complex included four other low-rise buildings, which were built in the early 1970s. The 47-story 7 World Trade Center building was added in the 1980s, to the north of the main complex. Altogether, the main World Trade Center complex occupied a 16-acre (65,000 m2) superblock.[68]

Criticism
Plans to build the World Trade Center were controversial. The site for the World Trade Center was the location of Radio Row, home to hundreds of commercial and industrial tenants, property owners, small businesses, and approximately 100 residents, many of whom fiercely resisted forced relocation.[69] A group of small businesses affected filed an injunction challenging the Port Authority's power of eminent domain.[70] The case made its way through the court system to the United States Supreme Court; the Court refused to accept the case.[71]

Private real estate developers and members of the Real Estate Board of New York, led by Empire State Building owner Lawrence A. Wien, expressed concerns about this much "subsidized" office space going on the open market, competing with the private sector when there was already a glut of vacancies.[72][73] The World Trade Center itself was not rented out completely until after 1979 and then only due to the fact that the complex's subsidy by the Port Authority made rents charged for its office space relatively cheaper than that of comparable office space in other buildings.[74] Others questioned whether the Port Authority should have taken on a project described by some as a "mistaken social priority".[75]

The World Trade Center design brought criticism of its aesthetics from the American Institute of Architects and other groups.[40][76] Lewis Mumford, author of The City in History and other works on urban planning, criticized the project and described it and other new skyscrapers as "just glass-and-metal filing cabinets".[77] The Twin Towers were described as looking similar to "the boxes that the Empire State Building and the Chrysler Building came in".[78] The twin towers' narrow office windows, only 18 inches (46 cm) wide and framed by pillars that restricted views on each side to narrow slots, were disliked by many.[39] Activist and sociologist Jane Jacobs also criticized plans for the WTC's construction, arguing that the waterfront should be kept open for New Yorkers to enjoy.[79]

The trade center's "superblock", replacing a more traditional, dense neighborhood, was regarded by some critics as an inhospitable environment that disrupted the complicated traffic network typical of Manhattan. For example, in his book The Pentagon of Power, Lewis Mumford denounced the center as an "example of the purposeless giantism and technological exhibitionism that are now eviscerating the living tissue of every great city".[80]

For many years, the immense Austin J. Tobin Plaza was often beset by brisk winds at ground level owing to the Venturi effect between the two towers.[81] In fact, some gusts were so high that pedestrian travel had to be aided by ropes.[82] In 1999, the outdoor plaza reopened after undergoing $12 million renovations, which involved replacing marble pavers with gray and pink granite stones, adding new benches, planters, new restaurants, food kiosks and outdoor dining areas.[83]

Most New Yorkers liked the congested, low-rise of yesteryear and thus hated the Twin Towers and everyone hated Venturi effect events.

World, National, State and city records



 * Tallest building in the world (both including and exclude the communication's mast)- 1971 to 1974.
 * Tallest building in the USA (both including and exclude the communication's mast)- 1972–1974
 * Tallest building in New York State 1971 (both including and exclude the communication's mast)- 2001.
 * Tallest building in New York City 1971 (both including and excluding the communication's mast)- 2001.
 * Fist place to be 'plane slammed', that is deliberately hit by a civil liner as a act of war or terrorism!
 * The fact that is stayed up any time after having such heavy damage as 9/11. The 1970s engineering was obviously of a good quality since they could not have foreseen 9/11 or been up to preparing for such an event with only 1970s technology, yet they made it strong enough not to instantly collapses on impact with the jets flown in to it!
 * Most 'sky lobbies'- 1971 to 1974.
 * Most elevators- 1971 to 1974.
 * Building with the most floors- 1972–2001.
 * Tallest twin towers in the world- 1972–1998.

1979
The fire fighting equipment and elevators were up-graded.

1983
Entrance video surveillance was added. The lift winding gears and firefighting equipment were upgraded.

1993-1994
The bomb damage was repaired and many places strengthened against any future attack. The ambient lighting upgraded in the car parks, basements, emergency stairwells, lifts and the PATH station. Part of the Marriot Hotel and all of it's car park and bacement were also heavly reinforced with high grade steel trusses and heavyer grade cement.

Complex facilities
The original World Trade Center was thought of as a North American cultural icon. At the time of their completion the "Twin Towers", the original 1 World Trade Center (the North Tower), at 417 metres (1,368 ft), and 2 World Trade Center (the South Tower), were the tallest buildings in the world. The other buildings in the complex included the Marriott World Trade Center (3 WTC), 4 WTC, 5 WTC, 6 WTC, and 7 WTC. All of these buildings were built between 1975 and 1985, with a construction cost of $400 million (equivalent to $2,300,000,000 in 2015 dollars). The complex was located in New York City's Financial District and contained 13,400,000 square feet (1,240,000 m2) of office space.

The World Trade Center experienced a fire on February 13, 1975, a bombing on February 26, 1993 and a robbery on January 14, 1998. In 1998, the Port Authority decided to privatize the World Trade Center, leasing the buildings to a private company to manage, and awarded the lease to Silverstein Properties in July 2001.

On a typical weekday 50,000 people worked in the towers with another 200,000 passing through as visitors. The complex was so large that it had its own zip code: 10048. The towers offered expansive views from the observation deck atop the South Tower and the Windows on the World restaurant on top of the North Tower. The Twin Towers became known worldwide, appearing in numerous movies and television shows as well as on postcards and other merchandise, and became seen as a New York icon, in the same league as the Empire State Building, Chrysler Building and the Statue of Liberty.

North and South Towers


One World Trade Center and Two World Trade Center, commonly the Twin Towers, the idea of which was brought up by Minoru Yamasaki, were designed as framed tube structures, which provided tenants with open floor plans, uninterrupted by columns or walls. They were the main buildings of the World Trade Center. The North Tower (One World Trade Center), the tallest building in the world at 1,368 feet (417 m) by the time of its completion, began construction in 1966 with the South Tower (2 World Trade Center); extensive use of prefabricated components helped to speed up the construction process, and the first tenants moved into the North Tower in December 1970, while it was still under construction. When completed in 1973, the South Tower, Two World Trade Center (the South Tower) became the second tallest building in the world at 1,362 feet (415 m); the South Tower's rooftop observation deck was 1,362 ft (415 m) high and its indoor observation deck was 1,310 ft (400 m) high. Each tower stood over 1,350 feet (410 m) high, and occupied about 1 acre (4,000 m2) of the total 16 acres (65,000 m2) of the site's land. During a press conference in 1973, Yamasaki was asked, "Why two 110-story buildings? Why not one 220-story building?" His tongue-in-cheek response was: "I didn't want to lose the human scale."

WTC South Tower Lobby interior, overlooking the elevator core and red carpet from the balcony When completed in 1972, 1 World Trade Center became the tallest building in the world for two years, surpassing the Empire State Building after a 40-year reign. The North Tower stood 1,368 feet (417 m) tall and featured a telecommunications antenna or mast that was added at the top of the roof in 1978 and stood 362 feet (110 m) tall. With the 362-foot (110 m)-tall antenna/mast, the highest point of the North Tower reached 1,730 feet (530 m).[93] The World Trade Center towers held the height record only briefly, as Chicago's Sears Tower, finished in May 1973, reached 1,450 feet (440 m) at the rooftop. Throughout their existence, the WTC towers had more floors (at 110) than any other building. This number was not surpassed until the advent of the Burj Khalifa, which opened in 2010.

Of the 110 stories in both, eight were set aside for technical services in mechanical floors (floors 7/8, 41/42, 75/76, and 108/109), which are four two-floor areas that evenly spaced up the building. All the remaining floors were free for open-plan offices. Each floor of the towers had 40,000 square feet (3,700 m2) of space for occupancy. The original Two World Trade Center had 95 express and local elevators. The tower had 3,800,000 square feet (350,000 m2) of office space.

Sky Lobbies
A sky lobby is an intermediate interchange floor where people can change from an express elevator that stops only at the sky lobby to a local elevator which stops at every floor within a segment of the building. When designing very tall (supertall) buildings, supplying enough elevators is a problem – travellers wanting to reach a specific higher floor may conceivably have to stop at a very large number of other floors on the way up to let other passengers off and on. This increases travel time, and indirectly requires many more elevator shafts to still allow acceptable travel times – thus reducing effective floor space on each floor for all levels. (The other main technique to increase usage without adding more elevator shafts is double-deck elevators.)

Early uses of the sky lobby include the original Twin Towers of the World Trade Center and the John Hancock Center in Chicago.

Windows on the World restaurant


Windows on the World was a complex of venues at the top floors (106th and 107th) of the One World Trade Center\Original building\North Tower\Building One of the original World Trade Center in Lower Manhattan that included a restaurant called Windows on the World, a smaller restaurant called Wild Blue, a bar called The Greatest Bar on Earth, and rooms for private functions. Developed by restaurateur Joe Baum and designed initially by Warren Platner, Windows on the World occupied 50,000 square feet (4,600 m²) of space in the North Tower. The restaurants operated from April 19, 1976, until 2001 when they were destroyed in the September 11 attacks.

The Windows on the World was a complex of venues at the top floors (106th and 107th) of the North Tower (Building One) of the original World Trade Center in Lower Manhattan that included a restaurant called Windows on the World, a smaller restaurant called Wild Blue, a bar called The Greatest Bar on Earth, and rooms for private functions. Developed by restaurateur Joe Baum and designed initially by Warren Platner, Windows on the World occupied 50,000 square feet (4,600 m²) of space in the North Tower. The restaurants operated from April 19, 1976, until 2001 when they were destroyed in the September 11 attacks.

It has been speculated that The Falling Man, a famous photograph of a man dressed in white falling headfirst on September 11, was an employee at Windows on the World, but his identity has never been conclusively established, although he was believed to be Jonathan Briley.

Top of the World observation deck


Although most of the space in the World Trade Center complex was off-limits to the public, the South Tower featured an indoor and outdoor public observation area called Top of the World Trade Center Observatories on its 107th and 110th floors. Visitors would pass through security checks added after the 1993 World Trade Center bombing, then were sent to the 107th floor indoor observatory at a height of 1,310 feet (400 m). The columns on each face of the building were narrowed on this level to allow 28 inches of glass between them. The Port Authority renovated the observatory in 1995, then leased it to Ogden Entertainment to operate.

Attractions added to the observation deck included a simulated helicopter ride around the city. The 107th floor food court was designed with a subway car theme and featured Sbarro and Nathan's Famous Hot Dogs. Weather permitting, visitors could take two short escalator rides up from the 107th floor viewing area to an outdoor viewing platform on the 110th floor at a height of 1,377 ft (420 m). On a clear day, visitors could see up to 50 miles (80 km). An anti-suicide fence was placed on the roof itself, with the viewing platform set back and elevated above it, requiring only an ordinary railing and leaving the view unobstructed, unlike the observation deck of the Empire State Building.

Other buildings
Five smaller buildings stood around the 16 acres (65,000 m2) block. One was the 22-floor hotel, which opened in 1981 as the Vista Hotel, and in 1995 became the Marriott World Trade Center (3 WTC) at the southwest corner of the site. Three low-rise buildings (4 WTC, 5 WTC, and 6 WTC) in the same hollow tube design as the towers also stood around the plaza. 6 World Trade Center, at the northwest corner, housed the United States Customs Service and the U.S. Commodities Exchange. 5 World Trade Center was located at the northeast corner above the PATH station and 4 World Trade Center was at the southeast corner. In 1987, a 47-floor office building called 7 World Trade Center was built north of the block. Beneath the World Trade Center complex was an underground shopping mall, which in turn had connections to various mass transit facilities including the New York City Subway system and the Port Authority's own PATH trains connecting Manhattan to New Jersey.

In-house bank vault
One of the world's largest gold depositories was stored underneath the World Trade Center, owned by a group of commercial banks. The 1993 bombing detonated close to the vault. Seven weeks after the September 11 attacks, $230 million in precious metals was removed from basement vaults of 4 WTC, which included 3,800 100-Troy-ounce 24 carat gold bars and 30,000 1,000-ounce silver bars.

In-house police station
Due to it's size, economic activity, demographic profile, security issues and working population, it needed a small in-house NYPD police station.

World Trade Center station (PATH)
World Trade Center is a terminal station in Lower Manhattan for PATH rail service. It was originally opened on July 19, 1909, as Hudson Terminal, but was torn down, rebuilt as World Trade Center, and re-opened July 6, 1971. Following the September 11, 2001 attacks, a temporary station opened in 2003.

This station serves as the terminus for the Newark – World Trade Center and Hoboken – World Trade Center routes. The main station house, the Oculus, opened on March 4, 2016, and the terminal was renamed the World Trade Center Transportation Hub, or World Trade Center for short.

Groundbreaking on the World Trade Center took place in 1966. The site was on landfill, with bedrock located 65 metres (213 ft) below the surface. A new method was used to construct a slurry wall to keep water from the Hudson River out. During excavation of the site and construction of the towers, the original Hudson Tubes remained in service as elevated tunnels. The Hudson Terminal was shut down in 1971 when a new Port Authority Trans-Hudson, or PATH Railroad station was completed. The new station cost $35 million to build. At the time, it had a passenger volume of 85,000 daily. The complex was located in New York City's Financial District and contained 13,400,000 square feet (1,240,000 m2) of office space.

Also, the M5  New York City Bus route runs northbound on Church Street and southbound to South Ferry on Broadway.

The station did not sustain significant damage during the 1993 World Trade Center bombing, although a section of ceiling in the station collapsed and trapped dozens. Within a week, the Port Authority was able to resume PATH service to the World Trade Center.

By 2001, the volume of passengers using the WTC PATH station was approximately 25,000 daily.

February 13, 1975 fire
On February 13, 1975, a three-alarm fire broke out on the 11th floor of the North Tower. Fire spread through the tower to the 9th and 14th floors by igniting the insulation of telephone cables in a utility shaft that ran vertically between floors. Areas at the furthest extent of the fire were extinguished almost immediately and the original fire was put out in a few hours. Most of the damage was concentrated on the 11th floor, fueled by cabinets filled with paper, alcohol-based fluid for office machines, and other office equipment. The fireproofing protected the steel and there was no structural damage to the tower. In addition to damage caused by the fire on the 9th - 14th floors, water from the extinguishing of the fires damaged a few floors below. At that time, the World Trade Center had no fire fire sprinkler systems.

February 26, 1993, bombing
The first terrorist attack on the World Trade Center occurred on February 26, 1993, at 12:17 p.m. A Ryder truck filled with 1,500 pounds (680 kg) of explosives, planted by Ramzi Yousef, detonated in the underground garage of the North Tower. The blast opened a 100 foot (30 m) hole through five sublevels with the greatest damage occurring on levels B1 and B2 and significant structural damage on level B3. Six people were killed and 1,042 others were injured during escape attempts complicated by smoke infiltration from the base of the building up to the 93rd floor of both towers. Many people inside the North Tower were forced to walk down darkened stairwells that contained no emergency lighting, some taking two hours or more to reach safety.

Yousef fled to Pakistan after the bombing but was arrested in Islamabad in February 1995, and was extradited back to the United States to face trial. Sheikh Omar Abdel Rahman was convicted in 1996 for involvement in the bombing and other plots. Yousef and Eyad Ismoil were convicted in November 1997 for their carrying out the bombing. Four others had been convicted in May 1994 for their involvement in the 1993 bombing. According to a presiding judge, the conspirators' chief aim at the time of the attack was to destabilize the north tower and send it crashing into the south tower, toppling both landmarks.

Following the bombing, floors that were blown out needed to be repaired to restore the structural support they provided to columns. The slurry wall was in peril following the bombing and loss of the floor slabs that provided lateral support against pressure from Hudson River water on the other side. The refrigeration plant on sublevel B5, which provided air conditioning to the entire World Trade Center complex, was heavily damaged.After the bombing, the Port Authority installed photoluminescent markings in the stairwells. The fire alarm system for the entire complex needed to be replaced because critical wiring and signaling in the original system was destroyed. As a memorial to the victims of the bombing of the tower, a reflecting pool was installed with the names of those who had been killed in the blast. However, the memorial was destroyed following the September 11 attacks. Names of the victims of the 1993 bombing are included in the National September 11 Memorial & Museum.

January 14, 1998, robbery
In January 1998, Mafia member Ralph Guarino, who had gained maintenance access to the World Trade Center, arranged a three-man crew for a heist that netted over $2 million from a Brinks delivery to the eleventh floor of the World Trade Center.

Other events
French high wire acrobatic performer Philippe Petit walked between the towers on a tightrope in 1974, as shown in the documentary film Man on Wire and depicted in the feature film The Walk. Petit walked between the towers eight times on a steel cable.

Brooklyn toymaker George Willig scaled the exterior of the south tower in 1977.

In 1983, on Memorial Day, high-rise firefighting and rescue advocate Dan Goodwin successfully climbed the outside of the WTC's North Tower. His stunt was meant to call attention to the inability to rescue people potentially trapped in the upper floors of skyscrapers.

The 1995 PCA world chess championship was played on the 107th floor of the South Tower.

Lease
The Port Authority accepted a $3.25 billion for the 99-year lease from Vornado in early 2001.

Diplomacy
Between 1978 and 1995, the Consulate of Paraguay was located in Suite 1609 of One World Trade Center. Home Lines once occupied Suite 3969.

ZIP code
The building's address was One World Trade Center, with the WTC complex having its own ZIP code of 10048 due to its large size.

The 9/11 attacks
The September 11 attacks (also referred to as 9/11) were a series of four coordinated terrorist attacks by the Islamic terrorist group al-Qaeda on the United States on the morning of September 11, 2001. The attacks killed 2,996 people and injured over 6,000 others and caused at least $10 billion in property and infrastructure damage and $3 trillion in total costs.

Four passenger airliners operated by two major U.S. passenger air carriers (United Airlines and American Airlines)—all of which departed from airports on the northeastern United States bound for California—were hijacked by 19 al-Qaeda terrorists, losing one of their passports in the WTC area. Two of the planes, American Airlines Flight 11 and United Airlines Flight 175, were crashed into the North and South towers, respectively, of the World Trade Center complex in New York City. Within an hour and 42 minutes, both 110-story towers collapsed, with debris and the resulting fires causing partial or complete collapse of all other buildings in the World Trade Center complex, including the 47-story 7 World Trade Center tower, as well as significant damage to ten other large surrounding structures. A third plane, American Airlines Flight 77, was crashed into the Pentagon (the headquarters of the United States Department of Defense) in Arlington County, Virginia, thus leading to a partial collapse of the building's western side. The fourth plane, United Airlines Flight 93, initially was steered toward Washington, D.C., but crashed into a field in Stonycreek Township near Shanksville, Pennsylvania, after its passengers tried to overcome the hijackers. It was the deadliest incident for firefighters and law enforcement officers in the history of the United States, with 343 and 72 killed respectively.

Suspicion for the attack quickly fell on al-Qaeda. The United States responded to the attacks by launching the War on Terror and invading Afghanistan to depose the Taliban, which had harbored al-Qaeda. Many countries strengthened their anti-terrorism legislation and expanded the powers of law enforcement and intelligence agencies to prevent terrorist attacks. Although al-Qaeda's leader, Osama bin Laden, initially denied any involvement, in 2004 he claimed responsibility for the attacks. Al-Qaeda and bin Laden cited U.S. support of Israel, the presence of U.S. troops in Saudi Arabia, and sanctions against Iraq as motives. Having evaded capture for almost a decade, bin Laden was located and killed by SEAL Team Six of the U.S. military in May 2011.

The destruction of the World Trade Center and nearby infrastructure caused serious damage to the economy of Lower Manhattan and had a significant effect on global markets, closing Wall Street until September 17 and the civilian airspace in the U.S. and Canada until September 13. Many closings, evacuations, and cancellations followed, out of respect or fear of further attacks. Cleanup of the World Trade Center site was completed in May 2002, and the Pentagon was repaired within a year. On November 18, 2006, construction of One World Trade Center began at the World Trade Center site. The building was officially opened on November 3, 2014. Numerous memorials have been constructed, including the National September 11 Memorial & Museum in New York City, the Pentagon Memorial in Arlington County, Virginia, and the Flight 93 National Memorial in a field in Stonycreek Township near Shanksville, Pennsylvania.

Tenants at the time of the attacks
The tenant list below was compiled from the original list provided by CoStar Group (a provider of electronic commercial real estate information), and quoted by CNN and most media. It was amended using UnBlinking.com. Entries unique to UnBlinking are in italics, marked (?UB) if uncertain. Companies listed on different floors by each source are marked (CS) at their position in CoStar, and (UB) at their position in UnBlinking. Special cases link to footnotes for more explanations. Cantor Fitzgerald's corporate headquarters were located in One World Trade Center.

The attacks them selves


Early on the morning of September 11, 2001, 19 hijackers took control of four commercial airliners (two Boeing 757 and two Boeing 767) en route to California (three headed to LAX in Los Angeles, and one to SFO in San Francisco) after takeoffs from Logan International Airport in Boston, Massachusetts; Newark Liberty International Airport in Newark, New Jersey; and Washington Dulles International Airport in Loudoun and Fairfax counties in Virginia. Large planes with long flights were selected for hijacking because they would be 'heavily fueled' (carry most of thire fule due to a recent take-off).

 The four flights were:  Media coverage was extensive during the attacks and aftermath, beginning moments after the first crash into the World Trade Center.
 * 1) American Airlines Flight 11: a Boeing 767 aircraft, departed Logan Airport at 7:59 a.m. en route to Los Angeles with a crew of 11 and 76 passengers, not including five hijackers. The hijackers flew the plane into the North Tower of the World Trade Center in New York City at 8:46 a.m.
 * 2) United Airlines Flight 175: a Boeing 767 aircraft, departed Logan Airport at 8:14 a.m. en route to Los Angeles with a crew of nine and 51 passengers, not including five hijackers. The hijackers flew the plane into the South Tower of the World Trade Center in New York City at 9:03 a.m.
 * 3) American Airlines Flight 77: a Boeing 757 aircraft, departed Washington Dulles International Airport at 8:20 a.m. en route to Los Angeles with a crew of six and 53 passengers, not including five hijackers. The hijackers flew the plane into the Pentagon in Arlington County, Virginia, at 9:37 a.m.
 * 4) United Airlines Flight 93: a Boeing 757 aircraft, departed Newark International Airport at 8:42 a.m. en route to San Francisco, with a crew of seven and 33 passengers, not including four hijackers. As passengers attempted to subdue the hijackers, the aircraft crashed into a field in Stonycreek Township near Shanksville, Pennsylvania, at 10:03 a.m.

At 8:46 a.m., five hijackers crashed American Airlines Flight 11 into the northern façade of the World Trade Center's North Tower (1 WTC), and at 9:03 a.m., another five hijackers crashed United Airlines Flight 175 into the southern façade of the South Tower (2 WTC). Five hijackers flew American Airlines Flight 77 into the Pentagon at 9:37 a.m. A fourth flight, United Airlines Flight 93, under the control of four hijackers, crashed near Shanksville, Pennsylvania, southeast of Pittsburgh, at 10:03 a.m. after the passengers fought the hijackers. Flight 93's target is believed to have been either the Capitol or the White House.

Flight 93's cockpit voice recorder revealed crew and passengers tried to seize control of the plane from the hijackers after learning through phone calls that Flights 11, 77, and 175 had been crashed into buildings that morning. Once it became evident to the ruthless hijackers that the passengers might regain control of the plane, the hijackers spitefully rolled the plane and thus intentionally crashed it.

Three buildings in the World Trade Center collapsed due to fire-induced structural failure. The South Tower collapsed at 9:59 a.m. after burning for 56 minutes in a fire caused by the impact of United Airlines Flight 175 and the explosion of its fuel. The North Tower collapsed at 10:28 a.m. after burning for 102 minutes. When the North Tower collapsed, debris fell on the nearby 7 World Trade Center building (7 WTC), damaging it and starting fires. These fires burned for hours, compromising the building's structural integrity, and 7 WTC collapsed at 5:21 p.m. The west side of the Pentagon sustained significant damage.

Many of the surrounding buildings were also either damaged or destroyed as the towers fell. 5 WTC suffered a large fire and a partial collapse of its steel structure. Other buildings destroyed include St. Nicholas Greek Orthodox Church, Marriott World Trade Center (Marriott Hotel 3 WTC), South Plaza (4 WTC), and U.S. Customs (6 WTC). The World Financial Center buildings, 90 West Street, and 130 Cedar Street suffered fires. The Deutsche Bank Building, the Verizon Building, and World Financial Center 3 suffered impact damage from the towers' collapse, as did 90 West Street. One Liberty Plaza survived structurally intact but sustained surface damage including shattered windows. 30 West Broadway was damaged by the collapse of 7 WTC. The Deutsche Bank Building, which was covered in a large black "shroud" after September 11 to cover the building's damage, was deconstructed because of water, mold, and other severe damage caused by the neighboring towers' collapse.


 * 1) Collapse of the South Tower
 * 2) Collapse of the North Tower
 * 3) Collapse of 7 World Trade Center
 * 4) St. Nicholas Greek Orthodox Church,
 * 5) Marriott World Trade Center (Marriott Hotel 3 WTC),
 * 6) South Plaza (4 WTC)
 * 7) U.S. Customs (6 WTC).

Global response


Reactions to the September 11 attacks included condemnation from world leaders, other political and religious representatives and the international media, as well as numerous memorials and services all over the world. The attacks were widely condemned by the governments of the world, including those traditionally considered hostile to the United States, such as Cuba, Iran, Libya, and North Korea. However, in a few cases celebrations of the attacks were also reported, and some groups and individuals accused the United States in effect of bringing the attacks on itself.

Iraq's government initially supported it, as did the majority of the people in Sunni Central Iraq, Saudi Arabia, Palestine, Jordan, southern England, central Scotland and Pakistan's tribal territories (especial Waziristan) on the Afghan border).

Many countries introduced anti-terrorism legislation and froze the bank accounts of businesses and individuals they suspected of having connections with al-Qaeda and its leader Osama bin Laden, the accused perpetrators of the attacks.

United Nations Security Council Resolution 1368 condemned the attacks, and expressed readiness to take all necessary steps to respond and combat all forms of terrorism in accordance with their Charter. Numerous countries introduced anti-terrorism legislation and froze bank accounts they suspected of al-Qaeda ties. Law enforcement and intelligence agencies in a number of countries arrested alleged terrorists.

The NATO casus foederis is enacted
Article 5 of the NATO treaty is it's casus foederis. It commits each member state to consider an armed attack against one member state to be an armed attack against them all. It was invoked only once so far and it was done by the United States after the September 11 attacks in 2001. Apparently, the governments of Spain, Portugal, the Netherlands, Luxembourg and Denmark showed no overt sympathy to the USA or any condemnation of the attacks, unlike their citizens. If they did not actually offer any covert help either and really meant to see America swing, then they thus breached the treaty's mutual defense aspect. The UK, Australia, New Zealand, Germany, Italy, Portugal, Greece, the USA, Canada, France, Israel and Turkey increased there diplomatic and espionage activity in the Middle East activate in order to stop any immediate threats to U.S. assets in the region.

Eurosceptics still maintain the 9\11 attacks were faked by the American government, were not any were as bad as they are said to be, were a heroic blow for freedom, were a Israeli/Jewish plot and or a de facto comedic event\ de jure legal rather than a blood thirsty war crime.

The UN's opinion on flying civil aircraft in to buildings\'plain slamming'
The UN regards events like 9\11 as illegal because it is horrifically indiscriminate and lethal. Most British people (especially Eurosceptics) have yet to realize this and regard the horrific, dishonest, indiscriminate and\or disproportionate use of force as legitimate, appropriate, cool and\or comedic.

Death toll, material losses and fiscal losses
The Twin Towers of the World Trade Center collapsed on September 11, 2001, as a result of being struck by two jet airliners hijacked by 10 terrorists affiliated with al-Qaeda during the September 11 attacks. Two of the four hijacked airliners crashed into the Twin Towers, one into the North Tower (1 World Trade Center) and the other into the South Tower (2 World Trade Center). The collapse of the Twin Towers destroyed the rest of the complex, and debris from the collapsing towers severely damaged or destroyed more than a dozen other adjacent and nearby structures. The South Tower collapsed at 9:59 am, less than an hour after being hit by the second hijacked airliner, and at 10:28 am the North Tower collapsed. Later that day, 7 World Trade Center collapsed at 5:21 pm from fires that had started when the North Tower collapsed. As a result of the attacks to the towers, a total of 2,763 people died. Of the people who died in and within the towers, 2,192 were civilians, 343 were firefighters, and 71 law enforcement officers. Aboard the two airplanes, 147 civilians and 10 hijackers also died.

The Falling Man photograph
The Falling Man is a photograph taken by Associated Press photographer Richard Drew of a man falling from the North Tower of the World Trade Center at 9:41:15 a.m. during the September 11 attacks in New York City. The subject of the image, whose identity remains uncertain, was one of the people trapped on the upper floors of the skyscraper who either fell searching for safety or jumped to escape the fire and smoke. At least 200 people are believed to have fallen or jumped to their deaths that day while other estimates say the number is half of that or fewer. Officials could not recover or identify the bodies of those forced out of the buildings prior to the collapse of the towers. All deaths in the attacks except those of the hijackers were ruled to be homicides due to blunt trauma (as opposed to suicides). The New York City medical examiner's office said it does not classify the people who fell to their deaths on September 11 as "jumpers": "A 'jumper' is somebody who goes to the office in the morning knowing that they will commit suicide. These people were forced out by the smoke and flames or blown out."

The photograph gives the impression that the man is falling straight down; however, a series of photographs taken of his fall showed him to be tumbling through the air.

The photographer has noted that, in at least two cases, newspaper stories commenting on the image have attracted a barrage of criticism from readers who found the image "disturbing".

Lost artworks
Many works of art were destroyed in the collapse.
 * Ideogram (1967) stainless steel sculpture by James Rosati
 * Cloud Fortress (1975) a large, black granite piece by Japanese artist Masayuki Nagare, destroyed in the 9/11 rescue and recovery efforts.
 * The World Trade Center Tapestry a 20' x 35' tapestry by Joan Miró that hung in the South Tower Lobby.
 * Sky Gate, New York (1977–78) large wooden sculpture by Louise Nevelson
 * A memorial fountain for the victims of the 1993 World Trade Center bombing by Elyn Zimmerman
 * World Trade Center Stabile (1971) a 25' red steel sculpture by Alexander Calder. Approximately 30% of the sculpture was recovered.
 * Some 300 sculptures and drawings by Auguste Rodin, part of the Cantor Fitzgerald collection.
 * Needle Tower (1968) by Kenneth Snelson.
 * Recollection Pond, a tapestry by Romare Bearden.
 * Path Mural, by Germaine Keller.
 * Commuter Landscape, a large mural by Cynthia Mailman.
 * Fan Dancing with the Birds, a mural by Hunt Slonem.
 * The Entablature Series by Roy Lichtenstein
 * Approximately 40,000 negatives of photographs by Jacques Lowe documenting the presidency of John F. Kennedy.
 * The Sphere, an abstract sculpture by Fritz Koenig, survived the collapse but was seriously damaged, and now serves as a memorial.

Many other works of art and valuable artifacts, found in safe deposit boxes located throughout the towers, were also destroyed. Two other sculptures were damaged, but not destroyed by the attacks. These are Red Cube by Isamu Noguchi and Joie de Vivre by Mark di Suvero, located down the street from the World Trade Center. They were repaired and still stand today.

Immediate response


At 8:32 a.m., FAA officials were notified Flight 11 had been hijacked and they in turn notified the North American Aerospace Defense Command (NORAD). NORAD scrambled two F-15s from Otis Air National Guard Base in Massachusetts and they were airborne by 8:53 a.m. Because of slow and confused communication from FAA officials, NORAD had 9 minutes' notice that Flight 11 had been hijacked, and no notice about any of the other flights before they crashed. After both of the Twin Towers had already been hit, more fighters were scrambled from Langley Air Force Base in Virginia at 9:30 a.m. At 10:20 a.m. Vice President Dick Cheney issued orders to shoot down any commercial aircraft that could be positively identified as being hijacked. However, these instructions were not relayed in time for the fighters to take action. Some fighters took to the air without live ammunition, knowing that to prevent the hijackers from striking their intended targets, the pilots might have to intercept and crash their fighters into the hijacked planes, possibly ejecting at the last moment.

For the first time in U.S. history, SCATANA was invoked, thus stranding tens of thousands of passengers across the world. The FAA closed American airspace to all international flights, causing about five hundred flights to be turned back or redirected to other countries. Canada received 226 of the diverted flights and launched Operation Yellow Ribbon to deal with the large numbers of grounded planes and stranded passengers.

The 9/11 attacks had immediate effects upon the American people. Police and rescue workers from around the country took leaves of absence, traveling to New York City to help recover bodies from the twisted remnants of the Twin Towers. Blood donations across the U.S. surged in the weeks after 9/11.

The deaths of adults in the attacks resulted in over 3,000 children losing a parent. Subsequent studies documented children's reactions to these actual losses and to feared losses of life, the protective environment in the aftermath of the attacks, and effects on surviving caregivers.

Initial opinions and analysis


In the immediate aftermath of the attacks, numerous structural engineers and experts spoke to the media, describing what they thought caused the towers to collapse. Abdolhassan Astaneh-Asl, a structural engineering professor at the University of California at Berkeley, explained that the high temperatures in the fires weakened the steel beams and columns, causing them to become "soft and mushy", and eventually they were unable to support the structure above. Astaneh also suggested that the fireproofing became dislodged during the initial aircraft impacts. He also explained that, once the initial structural failure occurred, progressive collapse of the entire structure was inevitable. Cesar Pelli, who designed the Petronas Towers in Malaysia and the World Financial Center in New York, remarked, "no building is prepared for this kind of stress."

On September 13, 2001, Zdeněk Bažant, professor of civil engineering and materials science at Northwestern University, circulated a draft paper with results of a simple analysis of the World Trade Center collapse. Bažant suggested that heat from the fires was a key factor, causing steel columns in both the core and the perimeter to weaken and experience deformation before losing their carrying capacity and buckling. Once more than half of the columns on a particular floor buckled, the overhead structure could no longer be supported and complete collapse of the structures occurred. Bažant later published an expanded version of this analysis. Other analyses were conducted by MIT civil engineers Oral Buyukozturk and Franz-Josef Ulm, who also described a collapse mechanism on September 21, 2001. They later contributed to an MIT collection of papers on the WTC collapses edited by Eduardo Kausel called The Towers Lost and Beyond.

The aftermath of the 9/11 attack resulted in immediate responses to the event, including domestic reactions, hate crimes, Muslim responses to the event, international responses to the attack, and military responses to the events. An extensive compensation program was quickly established by Congress in the aftermath to compensate the victims and families of victims of the 9/11 attack as well.

The terrorists' Motives
Osama bin Laden's declaration of a holy war against the United States, and a 1998 fatwā (a holy death warrant) signed by bin Laden and others, calling for the killing of Americans, are seen by investigators as evidence of his motivation. In bin Laden's November 2002 "Letter to America", he explicitly stated that al-Qaeda's motives for their attacks include:


 * 1) U.S. support of Israel.
 * 2) support for the "attacks against Muslims" in Somalia.
 * 3) support of Russian "atrocities against Muslims" in Chechnya.
 * 4) pro-American governments in the Middle East (who "act as your agents") being against Muslim interests.
 * 5) support of Indian "oppression against Muslims" in Kashmir.
 * 6) the presence of U.S. troops in Saudi Arabia.
 * 7) the sanctions against Iraq.

Others have argued that 9/11 was a strategic move with the objective of provoking America into a war that would incite a pan-Islamic revolution.

4 plausible conspiracy theories

 * 1) The CIA ran Ossama BinLardin, did 9\11 as a black opps to justify invading the Gulf, in which Ossama would be betrayed and liquidated.
 * 2) The Twin Towers collapsed downwards (pancaking) instead of sideways in to the path of the aircraft like a tree falling on to the side the wedge is cut out of or away from them like a tree falling away from were a wedge is driven in to it.
 * 3) The American establishment ignored Pakistani, Saudi, Iranian, British, Libyan Northern Alliance of Afghanistan and Malaysian security services' rumors and hints, as well as a few cryptic comments by Saddam Hussies and the Taliban.
 * 4) The Twin Towers were disinged not to collapses due to the intrinsic value of how skyscrapers are made. The tops would have come down as well as the stuff that got blown up, but not a 100% collapses in to the foundations unless it was bombed at ground level.

Memorials


Windows of Hope Family Relief Fund was organized soon after the attacks to provide support and services to the families of those in the food, beverage, and hospitality industries who had been killed on September 11 in the World Trade Center. Windows on the World executive chef Michael Lomonaco and owner-operator David Emil were among the founders of that fund.

The first memorials to the victims of the September 11 attacks in 2001 began to take shape online, as hundreds of webmasters posted their own thoughts, links to the Red Cross and other rescue agencies, photos, and eyewitness accounts. Numerous online September 11 memorials began appearing a few hours after the attacks, although many of these memorials were only temporary. Around the world, U.S. embassies and consulates became makeshift memorials as people came out to pay their respects.

The Tribute in Light was the first major physical memorial at the World Trade Center site. A permanent memorial and museum, the National September 11 Memorial & Museum at the World Trade Center, were built as part of the design for overall site redevelopment. The Memorial consists of two massive pools set within the original footprints of the Twin Towers with 30-foot (9.1 m) waterfalls cascading down their sides. The names of the victims of the attacks are inscribed around the edges of the waterfalls. Other permanent memorials are being constructed around the world.

In December 2001, a temporary viewing platform at Fulton Street, between Church Street and Broadway, opened to the public.

On March 11, 2002, 88 searchlights were installed and arranged to form two beams of light shooting straight up into the sky. This is called the Tribute in Light, and was originally lit every day at dusk until April 14, 2002. After that, the lights were lit on the two-year anniversary of the attack and have been lit on each subsequent September 11 since then.

One of the places that saw many memorials and candlelight vigils was Pier A in Hoboken, New Jersey, directly across from the World Trade Center. There was also a memorial service on March 11, 2002, at dusk on Pier A when the Tribute in Light first turned on, marking the half-year anniversary of the terrorist attack. A permanent September 11 memorial for Hoboken, called Hoboken Island, was chosen in September 2004.

In August 2008, New York City firefighters donated a cross made of steel from the World Trade Center to the Shanksville Volunteer Fire Company.[19] The beam, mounted atop a platform shaped like the Pentagon, was erected outside the Shanksville firehouse near the crash site of United Airlines Flight 93.

Replacement building
The entire World Trade Center site was destroyed in the terrorist attacks of September 11, 2001; One World Trade Center was the first of the famous Twin Towers to be struck by a hijacked aircraft, at 8:46 a.m EDT, and the second tower to collapse, at 10:28 a.m. Of the 2,977 victims killed in the attacks, 1,402 were in or above the North Tower impact zone. The North Tower was replaced by the present-day One World Trade Center tower, which was opened in November 2014 as the lead building of the redeveloped World Trade Center site.

At 1,776 feet tall, the One World Trade Center is currently (as of 2016) the tallest building in the Western Hemisphere. The new office block was also developed by The Port Authority of New York and New Jersey.

Over the following years, plans were created for the reconstruction of the World Trade Center. The Lower Manhattan Development Corporation (LMDC), established in November 2001 to oversee the rebuilding process, organized competitions to select a site plan and memorial design. Memory Foundations, designed by Daniel Libeskind, was selected as the master plan; however, substantial changes were made to the design.

The first new building at the site was 7 WTC, which opened in May 2006. The memorial section of the National September 11 Memorial & Museum opened on September 11, 2011 and the museum opened in May 2014. 1 WTC opened on November 3, 2014; 4 WTC opened on November 13, 2013; and 3 WTC is under construction and expected to open in 2017. As of November 2013, according to an agreement made with Silverstein Properties Inc., the new 2 WTC will not be built to its full height until sufficient leasing is established to make the building financially viable. In Summer 2015, Silverstein Properties revealed plans for a redesigned Tower 2 with News Corp as the core tenant; the Bjarke Ingels-designed structure was expected to be finished by 2020. 5 WTC will be developed by the Port Authority of New York and New Jersey, but, as of February 2014, a schedule was not confirmed.

Park51
Park51 (originally named Cordoba House) was to be a 13-story Islamic community center in Lower Manhattan including a "Muslim community center and a mosque." The developers hoped to promote an interfaith dialogue within the greater community. Due to its location two blocks from the World Trade Center site, it has been widely and controversially referred to as the "Ground Zero mosque". Numerous commentators disputed that characterization.

Park51 would have replaced an existing 1850s building of Italianate style that was damaged in the September 11 attacks. The design included a 500-seat auditorium, theater, a performing arts center, a fitness center, a swimming pool, a basketball court, a childcare area, a bookstore, a culinary school, an art studio, a food court, and a memorial to the victims of the September 11 attacks. It included a prayer space for the Muslim community to accommodate 1,000–2,000 people. Park51 was designed by the Principal of SOMA, Michel Abboud, who wrestled for months with a key problem to make the building fit naturally into its surrounds in lower Manhattan: on the one hand, it should have a contemporary design, and, at the same time, it should look Islamic.

In late September 2011, a temporary 4,000-square-foot (370 m2) Islamic center opened in renovated space at the Park51 location. In summer 2014, it was announced that there will instead be a 3-story museum with a prayer space, as well as condos, at 49-51 Park Place. In September 2015, it was reported that the owner of the site now plans to build a 667-foot, 70-story luxury condominium building at the site to take advantage of the booming residential real estate market in Lower Manhattan.

9/11 (film)
9/11 is a 2002 French-American documentary film about the September 11 attacks in New York City, in which two planes crashed into the buildings of the World Trade Center.

Other world trade centers

 * World Trade Center (1973–2001), the building complex that was destroyed by hijackers using airplanes on September 11, 2001
 * World Trade Center (2001–present)
 * One World Trade Center, the main building in the rebuilt complex
 * World Trade Center site
 * Dubai World Trade Centre
 * Trade center, a building dedicated to international trade
 * World Trade Center Chittagong
 * World Trade Center (Portland, Oregon)
 * List of world trade centers
 * Category:World Trade Centers

Also see

 * 1) Famous buildings
 * 2) CIS Tower
 * 3) 7 World Trade Center
 * 4) The Pentagon
 * 5) The White House
 * 6) Cheyenne Mountain Air Force Station (combat operations center)
 * 7) Pennsylvania Station (1910–63)
 * 8) Terrorism
 * 9) Civil aircraft