|World Trade Center|
The World Trade Center's Twin Towers
World Trade Center was the world's tallest building from 1972 to 1973.*
|Preceded by||Empire State Building|
|Surpassed by||Sears Tower|
|Location||New York City, NY, U.S.|
|Status||Destroyed on September 11, 2001|
|Antenna/Spire||1,727 ft (526.3 m) |
|Roof||1,368 ft (417.0 m)|
|Top floor||1,355 ft (413.0 m)|
|Floor area||8.6 million sq ft |
800,000 m² (1 & 2)
|Elevator count||198 (1 & 2)|
|Architect||Minoru Yamasaki, Emery Roth & Sons|
|Leslie Robertson, Leslie E. Robertson Associates|
|Contractor||Tishman Realty & Construction Company|
|Owner||Port Authority of New York and New Jersey|
*Fully habitable, self-supported, from main entrance to highest structural or architectural top; see the list of tallest buildings in the world for other listings.
The World Trade Center in New York City, United States (sometimes informally referred to as the WTC or the Twin Towers) was a complex of seven buildings in Lower Manhattan that were attacked by terrorists on the day of 9/11/2001. It was mostly designed by Detroit-based architect Minoru Yamasaki and engineer Leslie Robertson and developed by the Port Authority of New York and New Jersey. It was initiated in 1960 by a Lower Manhattan Association created and chaired by David Rockefeller, who had the original idea of building the center, with strong backing from the then-New York governor, his brother Nelson Rockefeller. The World Trade Center, New York, like most World Trade Centers located around the globe, belonged to the family of World Trade Centers Association. Prior to its destruction, Larry Silverstein held the most recent lease to the complex, the Port Authority having leased it to him in July 2001. The complex, located in the heart of New York City's downtown financial district, contained 13.4 million square feet (1.24 million m²) of office space, almost four percent of Manhattan's entire office inventory at that time.
Best known for its iconic 110-story twin towers (101 usable floors, eight engineering-only "service" floors on top of a lobby which was six stories high and 80') the World Trade Center was beset by a fire on February 13, 1975 and a bombing on February 26, 1993.
All seven original buildings in the complex were destroyed during the September 11 attacks. Three of the buildings collapsed: One World Trade Center (1 WTC, the North Tower), Two World Trade Center (2 WTC, the South Tower), and 7 World Trade Center (7 WTC). The Marriott World Trade Center (3 WTC) was crushed by the collapses of 1 WTC and 2 WTC. 4 World Trade Center (4 WTC), 5 World Trade Center (5 WTC), and 6 World Trade Center (6 WTC) were damaged beyond repair and later demolished. Three buildings not part of the complex were also destroyed: St. Nicholas Greek Orthodox Church was destroyed by the collapse of 2 WTC. The Deutsche Bank Building was damaged beyond repair by the explosions and collapse of 1 and 2 WTC; and Borough of Manhattan Community College's Fiterman Hall was damaged beyond repair by the collapse of 7 WTC; these are currently being deconstructed.
Planning and construction
During the post-World War II period, the United States thrived economically, with increasing international trade. At the time, economic growth in New York City was concentrated in Midtown Manhattan, with Lower Manhattan left out. To help stimulate urban renewal, David Rockefeller, with support from his brother, New York Governor Nelson Rockefeller, suggested that the Port Authority should build a "world trade center" in Lower Manhattan. Initial plans, made public in 1961, identified a site along the East River for the World Trade Center. Objections to the plan came from New Jersey Governor Robert B. Meyner, who resented that New York would be getting this $335 million project. Meanwhile, New Jersey's Hudson and Manhattan Railroad (H&M) was facing bankruptcy. Port Authority executive director, Austin J. Tobin agreed to take over control of the H&M Railroad, in exchange for support from New Jersey for the World Trade Center project.
With this acquisition, the Port Authority would obtain the Hudson Terminal, and decrepit buildings located above the terminal in Lower Manhattan. The Port Authority decided to demolish these buildings, and use this site along the Hudson River for the World Trade Center. The towers in the complex were designed by architect Minoru Yamasaki with Antonio Brittiochi and Emery Roth & Sons as associate architects. The World Trade Center was one of the most striking American implementations of the architectural ethic of Le Corbusier, as well as the seminal expression of Yamasaki's gothic modernist tendencies.
The World Trade Center included many structural engineering innovations in skyscraper design and construction. The towers were designed as framed tube structures. There was a frame of closely spaced columns tied together by deep spandrel beams along the exterior perimeter. The interior had 47 columns, all concentrated in the core. Engineer Felix Samuely used a similar concept in his "Mullion wall" buildings in the early 1950s as did Eero Saarinen in his US Embassy, London (1955-60); but these projects were low to medium rise and may not have been influences.
The perimeter columns supported virtually all lateral loads, such as wind loads, and shared the gravity loads with the core columns. All columns were founded on bedrock, which unlike Midtown Manhattan, where the bedrock is shallow, is at 65 feet (20m) below the surface. Above the seventh floor, there were 59 perimeter columns along each face of the building. The perimeter columns had a square cross section, 14 inches on a side (36 cm), and were constructed of welded steel plate. The thickness of the plates and grade of steel were varied over the height of the tower, ranging from 36 ksi to 100 ksi, with the steel strength and plate thickness decreasing with height. The perimeter structure was constructed with extensive use of prefabricated modular pieces, which consisted of three columns, three stories tall, connected together by spandrel plates. The spandrel plates were welded to the columns at the fabrication shop. The modular pieces were typically 52 inches (1.3 m) deep, and extended for two full floors and half of two more floors.
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, and served to transmit shear flow between columns, thus 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.
The building's core housed the elevator and utility shafts, restrooms, three stairwells, and other support spaces. The core in 1 WTC was oriented with the long axis east to west, while that of 2 WTC was oriented north to south. 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. The columns tapered with height, and consisted of welded box sections at lower floors and rolled wide-flange sections at upper floors. All of the elevators and stairwells were located in the core.
Prefabricated floor trusses bridged the large, column-free space between the perimeter and core. 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. A grid of lightweight bridging trusses and main trusses supported the floors. The trusses had a span of 60 feet (18.2 m) in the long-span areas and 35 feet (11.0 m) in the short span area. The trusses connected to the perimeter at alternate columns, and were therefore 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 spandel plates with vicsoelastic dampers, which helped reduce the amount of sway felt by building occupants. The trusses supported a 4-inch (10 cm) thick lightweight concrete floor slab, with shear connections for composite action.
Hat trusses (or "outrigger truss") located from the 107th floor to the top of the buildings were designed to support a tall communications antenna on top of each building, though only 1 WTC (north tower) actually had an antenna. The truss system consisted of six trusses along the long axis of 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.
To solve the problem of wind sway or vibration in the construction of the towers, chief engineer Leslie Robertson took a then unusual approach — instead of bracing the buildings corner-to-corner or using internal walls, the towers were essentially hollow steel tubes surrounding a central core and perimeter columns sharing the loads. The 208 feet (63.4 m) wide facade was, in effect, a prefabricated steel lattice, with columns on 39 inch (100 cm) centers acting as wind bracing to resist all overturning forces; the central core took the majority of the gravity loads of the building. A very light, economical structure was built by keeping the wind bracing in the most efficient area, the outside surface of the building, thus not transferring the forces through the floor membrane to the core, as in most curtain-wall structures. The core supported the weight of the entire building and the outer shell containing 240 vertical steel columns called around the outside of the building, which were bound to each other using ordinary steel trusses. In addition, 10,000 dampers were included in the structure. With the large core and high load-bearing perimeter for structural integrity, Robertson created a tower that was extremely light for its size.
The buildings were also the second supertall buildings to use sky lobbies, after the John Hancock Center in Chicago. Skylobbies are floors where commuters can switch from an express elevator that goes only to the sky lobbies to a local elevator that goes to each floor in a section. The local elevators were stacked on top of each other, 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 taking up a minimum of valuable office space. Altogether, the World Trade Center had 95 express and local elevators. 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.
The site of the World Trade Center was located on landfill, with the bedrock located 65 feet (20 m) below. In order to construct the World Trade Center, it was necessary to build the "bathtub", with the slurry wall along the West Street side of the site, which serves the purpose of keeping water from the Hudson River out. The slurry method involves digging a trench, and as excavation proceeds, filling the space with a "slurry" mixture, composed of bentonite, which plugs holes and keeps water out. When the trench was dug out, a steel cage was inserted, with concrete poured in, forcing the "slurry" out. The Port Authority’s chief engineer, John M. Kyle, Jr, devised the “slurry” method.
Groundbreaking for the construction of the World Trade Center was on August 5, 1966. The construction was under the auspices of the semiautonomous Port Authority of New York and New Jersey. Thirteen square blocks of low rise buildings in Radio Row, some of which predated the American Civil War, were razed to clear the site for construction.
The excavation of the foundations of the WTC complex, known as the Bathtub, was particularly complicated since there were two subway tubes close by needing protection without service interruption. A six-level basement was built in the foundations. The excavation of about 1 million cubic yards (760,000 m³) of earth and rock created a $90 million real estate asset for the project owner, the Port Authority of New York and New Jersey, which helped offset the enormous loss in revenues which came from the tax breaks given to the Trade Center itself. The soil was used to create 23 acres (93,000 m²) of landfill in the Hudson River next to the World Trade Center site, which became the site of Battery Park City (still under development).
In 1970, construction was completed on One World Trade Center, with its first tenants moving into the building in December 1970. Tenants first moved into Two World Trade Center in January 1972. When the World Trade Center twin towers were completed, the total costs to the Port Authority had reached $900 million. The ribbon cutting ceremony was on April 4, 1973.
Although the towers became an undeniable symbol of New York City, they were not without flaws and were handicapped in many ways. Initially conceived (as the name suggests) as a complex dedicated to companies and organizations directly taking part in "world trade," they at first failed to attract the expected clientele. During the early years, various governmental organizations became key tenants of the World Trade Center, including the State of New York. It was not until the 1980s that the city's perilous financial state eased, after which an increasing number of private companies — mostly financial firms tied to Wall Street — became tenants.
Moreover, the trade center's "superblock", which replaced 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, the technical historian 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." On the other hand, Mr. Yamasaki saw the expanse as a focal point of serenity amidst the chaos of the city. The twin towers' narrow office windows, only 18 inches (460 mm) wide, were also disliked by many for impairing the view from the buildings. This design element reflected on Yamasaki's fear of heights and desire to make building occupants secure with narrow windows.
For many years, the immense Austin J. Tobin Plaza was unwelcoming, and often beset by brisk winds at the ground level. 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 and food kiosks, and outdoor dining areas. In later years, the plaza became a center for outdoor concerts and other activities.
The Twin Towers
Ultimately the complex came to consist of seven buildings, but its most notable features were the main twin towers. Each of the WTC towers had 110 stories. 1 WTC (the North Tower, which featured a massive 360-foot (110 m) high TV and radio antenna added in 1978) stood 1,368 feet (417 m) high, and 2 WTC (the South Tower, which contained the observation deck) was 1,362 feet (415 m) high. The length and breadth of the towers were 208 feet (63.4 m) x 208 feet (63.4 m). Although only Tower 1 featured an antenna, the structure of each building was designed to carry a broadcast mast, and in the basement of the complex, The Mall at the World Trade Center was Manhattan's largest mall until 9-11.
When completed in 1972, 1 WTC became the tallest building on Earth, unseating the Empire State Building after a 40-year reign. 2 WTC became the second tallest building in the world when completed in 1973. 2 WTC did not need these facilities, so it remained 1,362 feet (415 m). Regardless, the WTC towers held the height record only briefly. As the building neared completion in 1973, work had already begun on Chicago's Sears Tower, which ultimately reached 1,450 feet (442 m). With the World Trade Center's destruction, the Empire State Building again became the tallest building in New York, after spending almost 30 years as the third-tallest in the city.
The towers' sheer size was the subject of a joke during a press conference unveiling the landmarks. Minoru Yamasaki was asked: "Why two 110-story buildings? Why not one 220-story building?" His response was: "I didn't want to lose the human scale". Another popular joke among New York urbanites that died out late in the 1970s from overtelling was that the towers looked like the boxes in which the Chrysler Building and Empire State Building were packaged.
Of the 110 stories, eight were set aside for technical services (mechanical floors) Level B6/B5, Floors 7/8, 41/42, 75/76 and 108/109, in four two-floor areas evenly spread 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. Each tower had 3.8 million square feet (350,000 m²) of office space. Altogether the entire complex of seven buildings had 11.2 million square feet (1.04 km²) of space.
During the 1990s, approximately 500 companies had offices in the complex, including many financial companies such as Morgan Stanley, Aon Corporation, Salomon Brothers, as well as the Port Authority itself. Electrical service to the towers was supplied by Consolidated Edison (ConEd) at 13,800 volts. This service passed through the World Trade Center Primary Distribution Center (PDC) and sent up through the core of the building to electrical substations located on the mechanical floors. The substations "stepped" the 13,800 primary voltage down to 480/277 volt secondary power and further to 120/208 volt general power and lighting service. The complex also was served by emergency generators located in the sublevels of the towers and on the roof of 5 WTC.
The 110th Floor of 1 WTC (North Tower) housed commercial and public service radio & television transmission equipment. The roof of 1 WTC contained a vast array of transmission antennas, including the 360 ft (approx 110m) center antenna mast, which was rebuilt in 1999 by Dielectric Inc. to accommodate DTV. The center mast contained the television signals for almost all NYC television broadcasters: WCBS-TV 2, WNBC-TV 4, WNYW 5, WABC-TV 7, WWOR-TV 9 Secaucus, WPIX 11, WNET 13 Newark, WPXN-TV 31, and WNJU 47. It also had four NYC FM broadcasters on it as well: WPAT-FM 93.1, WNYC 93.9, WKCR 89.9, and WKTU 103.5. Access to the roof was controlled from the WTC Operations Control Center (OCC) located in the B1 level of 2 WTC.
The World Trade Center complex was protected by an extensive fire detection and voice evacuation paging system upgraded after the 1993 bombing. Fire Command Stations, staffed by Fire Safety Directors were located in the lobbies of each building and the Operations Control Center (OCC) monitored these systems. An extensive study of the performance of World Trade Center Fire Protection Systems was conducted by the National Institute of Standards and Technology (NIST) following 2001-09-11.
Observation deck and Windows on the World
Although most of the space in the WTC complex was off-limits to the public, 2 WTC (South Tower) featured a public observation area named "Top Of The World." When visiting the observation deck, visitors would first pass through security checks added after the 1993 World Trade Center bombing. Next, visitors were whisked to the 107th floor indoor observatory at a height of 1,310 feet (399 m) and greeted with a 360-degree view of the New York City skyline, and exhibitions including a three-dimensional scale model of Manhattan, and a simulated helicopter ride around the city. Weather permitting, visitors could take two short escalator rides up from the 107th floor and visit what was the world's highest outdoor viewing platform. At a height of 1,377 feet (420 m), visitors were able to take in a view of the North Tower and New York City unlike any other. On a clear day, visitors could see up to 49 miles (78 km) in any given direction. 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.
The North Tower (1 WTC) had a restaurant on the 107th floor called Windows on the World, which was an elegant restaurant known as a place for big celebrations, such as weddings. In its last full year of operation, 2000, Windows on the World reported revenues of $37.5 million, making it the highest-grossing restaurant in the United States.
The other buildings
Five smaller buildings stood around the 16-acre (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, that was crushed between the two towers. 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 WTC 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 Jersey City, Hoboken, and Newark.
One of the world's largest gold depositories was stored underneath the World Trade Center, owned by a group of commercial banks. The 1993 bomb detonated close to the vault, but it withstood the explosion, as did the towers. Seven weeks after the September 11 attacks, $230 million in precious metals were removed from basement vaults of 4 WTC, which included 3,800 100-Troy-ounce registered gold bars and 30,000 1,000-ounce silver bars.
Life of the World Trade Center
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 spectacular views from the observation deck (located on top of the South Tower) and the Windows on the World restaurant (located on top of the North Tower). The Twin Towers became known worldwide, appearing in movies, TV shows, postcards, merchandise, magazines and much more, and became a New York icon, in the same league as the Empire State Building and Statue of Liberty. French high wire acrobatic performer Philippe Petit walked between the towers on a tightrope in 1974, and Brooklyn toymaker George Willig scaled the south tower in 1977. The 1995 PCA world chess championship, between Garry Kasparov and Viswanathan Anand, was played on the 107th floor of the South Tower.
February 13, 1975 fire
On February 13, 1975, a three-alarm fire broke out on the 11th floor of the North Tower, with fire spreading through the core from the 9th to 14th floors where electrical wiring was damaged. The fire ignited the insulation of telephone cables in a utility shaft that ran vertically between floors. The fire spread to other floors through openings in the floor slabs that were used to carry phone wires. The fires on other floors were extinguished almost immediately, and the main fire was put out in a few hours. Most of the damage was concentrated on the 11th floor, with the fire fueled by cabinets filled with paper, alcohol-based fluid for office machines, and other office equipment. The fires on other floors were extinguished almost immediately, and the main fire was put out in a few hours. Fireproofing protected the steel from melting and there was no structural damage to the tower. Other than the damage caused by the fire, a few floors below suffered water damage from the extinguishing of the fires above. At that time, the World Trade Center was not equipped with sprinkler systems.
Bombing of February 26, 1993
On February 26, 1993 at 12:17 PM, a Ryder truck filled with 1,500 pounds (680 kg) of explosives was planted by Ramzi Yousef and detonated in the underground garage of the North Tower, opening a 100 foot (30 m) hole through 5 sublevels of concrete leaving six people dead and 50,000 other workers and visitors gasping for air in the shafts of the 110 story 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. As the Port Authority was a bistate agency, the towers were exempt from New York City building codes. Subsequent to the bombing The Port Authority installed emergency lighting in the stairwells. It is believed that this lighting saved many lives during the events of September 11, 2001.
In 1997 and 1998, six Islamist extremists were convicted and sentenced to life in prison for their roles in the 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.
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. Following the September 11, 2001 attacks, relief workers found a single fractured piece of the fountain etched with the word "John"; to date it is the only remaining part of the 1993 memorial that survived the collapse of the towers.
In 1998, plans were approved by the Port Authority to privatize the World Trade Center. In 2001, the Port Authority sought to lease the World Trade Center to a private entity. Bids for the lease came from Vornado Realty Trust, a joint bid between Brookfield Properties Corporation and Boston Properties, and a joint bid by Silverstein Properties and The Westfield Group. By privatizing the World Trade Center, it would be added to the city's tax rolls. The lease was also intended to raise funds for other Port Authority projects. On February 15, 2001, the Port Authority announced that Vornado Trust Realty had won the lease for the World Trade Center, paying $3.25 billion for the 99-year lease. Vornado Realty outbid Silverstein by $600 million, though Silverstein upped his offer to $3.22 billion. However, Vornado insisted on last minute changes to the deal, including a shorter 39-year lease, which the Port Authority considered nonnegotiable. Vornado later withdrew and Silverstein's bid for the lease to the World Trade Center was accepted on April 26, 2001, and closed on July 24, 2001.
September 11, 2001
On September 11, 2001 at 8:46 a.m. Eastern Time, Al Qaeda suicide hijackers crashed American Airlines Flight 11 into the northern facade of the North Tower. Seventeen minutes later, at 9:03 a.m., a second team of hijackers crashed United Airlines Flight 175 into the South Tower, which collapsed and disintegrated at 9:59 a.m. At 10:28 a.m., the North Tower collapsed and disintegrated. At 5:20 p.m., 7 World Trade Center collapsed due to uncontrolled fires causing structural failure. 3 World Trade Center, a Mariott hotel, was destroyed during the collapse of the two towers. The three remaining buildings in the WTC plaza sustained heavy damage from debris, and were ultimately demolished.
At the time of the incident, media reports suggested that tens of thousands might have been killed in the massacre, as on any given day upwards of 50,000 people could be inside the towers. Ultimately, 2,749  death certificates were filed relating to the 9/11 attacks, as of May 23, 2007. Of these, 1,614 (59%) were identified from recovered physical remains. 343 of these deaths were New York City Firemen, 84 were Port Authority Employees, of whom 37 were Police. Another 23 were New York City Police. Of all the people who were still in the towers when they collapsed only 20 of these people were pulled out alive. Morgan Stanley was the largest tenant in the World Trade Center, with approximately 2,500 employees in the South Tower and 1,000 in the North Tower. For the following 8½ months, the World Trade Center site cleanup and recovery continued 24 hours a day and involved thousands of workers.
Film and media
The World Trade Center was an iconic structure and has been featured in numerous films, as well as appearing in many television shows, cartoons, comic books, computer/video games and music videos. The events surrounding September 11 are portrayed in several documentaries and movies, including two major motion pictures made in 2006, Oliver Stone's World Trade Center and Paul Greengrass' United 93. Several movies released shortly after 9/11 digitally erased the Twin Towers from skyline shots, such as Spider-Man (film). As of 2007[update], most reruns of popular television shows have chosen to leave the Twin Towers in airings of the show such as cut scenes in Friends and episodes of The Simpsons. An exception to this is the opening intro to HBO's Sex and The City, which removed shots of the Towers as a mark of respect for the victims.
Rebuilding the World Trade Center
|This article or section contains information about expected future buildings or structures. |
Some or all of this information may be speculative, and the content may change as building construction begins.
|Planned rebuilding |
World Trade Center
|Freedom Tower (Tower 1)|
|200 Greenwich Street (Tower 2)|
|175 Greenwich Street (Tower 3)|
|150 Greenwich Street (Tower 4)|
|130 Liberty Street (Tower 5)|
|7 World Trade Center|
|Memorial and museum|
|World Trade Center Memorial|
The process of cleanup and recovery at the World Trade Center site took eight months. Debris was transported from the World Trade Center site to Fresh Kills on Staten Island, where it was further sifted. On May 30, 2002, a ceremony was held to officially mark the end of the cleanup efforts. In 2002, ground was broken on construction of a new 7 World Trade Center building, located just to the north of the main World Trade Center site. Since it was not part of the site master plan, Larry Silverstein was able to proceed without delay on rebuilding of 7 World Trade Center. On May 23, 2006, 7 World Trade Center officially opened.
With the main World Trade Center site, numerous stakeholders were involved, including Silverstein, as well as the Port Authority which in turn meant that the Governor of New York State, George Pataki, also had some authority. As well, the victims' families, people in the surrounding neighborhoods, Mayor Michael Bloomberg and others wanted input. The Lower Manhattan Development Corporation was established to coordinate the reconstruction of the World Trade Center site. The LMDC held a competition to solicit possible designs for the site. Memory Foundations by Daniel Libeskind was selected as the master plan for the World Trade Center site. The plan included the 1,776-foot (541 m) Freedom Tower, as well as a memorial and a number of other office towers. Out of the World Trade Center Site Memorial Competition, a design by Michael Arad and Peter Walker, entitled Reflecting Absence, was selected in January 2004 for the World Trade Center Memorial.
On March 13, 2006 workers arrived at the World Trade Center site to remove remaining debris and start surveying work. This marks the official start of construction of the WTC Memorial and Museum. In April 2006, the owner of the site, The Port Authority, and private developer Larry Silverstein reached a tentative agreement. The main elements of that agreement are that Silverstein ceded rights to develop the Freedom Tower and Tower Five in exchange for financing with Liberty Bonds for Tower Two, Three, and Four, which are considered the most marketable properties of the site. On April 27, 2006, a ground-breaking ceremony was held for the Freedom Tower.In May 2006, architects Richard Rogers and Fumihiko Maki were announced as the architects for Towers Three and Four, respectively. The final designs for Towers Two, Three and Four were unveiled on September 7, 2006. Tower Two, or 200 Greenwich Street, will have a roof height of 1,254 feet (382 m) and a 96-foot (29 m) tripod spire for a total of 1,350 feet (411 m). Tower Three, or 175 Greenwich Street will have a roof height of 1,155 feet (352 m) and an antennae height of 1,255 feet (383 m). Tower Four, or 150 Greenwich Street, will have an overall height of 946 feet (288 m). On June 22, 2007 the Port Authority of New York and New Jersey announced that JP Morgan Chase will build Tower 5, a 42-story building on Site 5 currently occupied by the Deutsche Bank Building. Kohn Pedersen Fox was officially chosen as the architect for the building on July 17, 2007.