World Trade Center


The original World Trade Center was a large complex of seven buildings in the Financial District of Lower Manhattan, New York City, United States. It opened on April 4, 1973, and was destroyed in 2001 during the September 11 attacks. At the time of their completion, the Twin Towers—the original 1 World Trade Center (the North Tower), at 1,368 feet (417 m), and 2 World Trade Center (the South Tower), at 1,362 feet (415.1 m)—were the tallest buildings in the world. Other buildings in the complex included the Marriott World Trade Center (3 WTC), 4 WTC, 5 WTC, 6 WTC, and 7 WTC. The complex contained 13,400,000 square feet (1,240,000 m2) of office space.

Arial view of WTC in March of 2001

The original complex in March 2001. The tower on the left, with antenna spire, was 1 WTC. The tower on the right was 2 WTC. All seven buildings of the WTC complex are partially visible. The red granite-clad building left of the Twin Towers was the original 7 World Trade Center. In the background is the East River.


Record height

Tallest in the world from 1971 to 1973

Preceded by

Empire State Building


Surpassed by

Willis Tower

General information



Architectural style

New Formalism


Lower Manhattan, New York City


40°42′42″N 74°00′45″W


August 5, 1966; 55 years ago

Construction started

1 WTC: August 6, 1968

2 WTC: January 1969

3 WTC: March 1979

4, 5, and 6 WTC: 1970

7 WTC: October 2, 1984


1 WTC: December 23, 1970

2 WTC: July 19, 1971


1 WTC: 1972

2 WTC: 1973

3 WTC: April 1, 1981

4 WTC: 1975

5 WTC: 1972

6 WTC: 1973

7 WTC: 1987


1 WTC: December 15, 1970

2 WTC: September 1971

3 WTC: July 1, 1981[1]

4 WTC: January 1977

5 WTC: March 1972

6 WTC: January 1974

7 WTC: May 1987


April 4, 1973; 48 years ago


September 11, 2001; 19 years ago


Port Authority of New York and New Jersey

Other information


Antenna spire 1 WTC: 1,728 feet (526.7 m)


1 WTC: 1,368 feet (417.0 m)

2 WTC: 1,362 feet (415.1 m)

3 WTC: 250 feet (76.2 m)

4 and 5 WTC: 120 feet (36.6 m)

6 WTC: 110 feet (33.5 m)

7 WTC: 610 feet (185.9 m)

Top floor 

1 WTC: 1,355 feet (413 m)

2 WTC: 1,348 ft (411 m)

Technical details

Floor count 

1 and 2 WTC: 110 floors

3 WTC: 22 floors

4 and 5 WTC: 9 floors

6 WTC: 8 floors

7 WTC: 47 floors

Floor area 

1 and 2 WTC: 4,300,000 sq ft (400,000 m2) each

4, 5, and 6 WTC: 500,000 sq ft (50,000 m2) each

7 WTC: 1,868,000 sq ft (170,000 m2)

Lifts/elevators 1 and 2 WTC: 99 each

Design and construction


Minoru Yamasaki

Emery Roth & Sons


Port Authority of New York and New Jersey


• Worthington, Skilling, Helle & Jackson

• Leslie E. Robertson Associates

Main contractor

Tishman Realty & Construction Company.


Establishment of World Trade Center

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 there.

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; or the west side, near the Hudson and Manhattan Railroad (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.

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At the time, ridership on New Jersey’s H&M Railroad 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 H & M Railroad. They 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 the Port Authority’s acquisition of the H&M Railroad, New Jersey agreed to support the World Trade Center project. As part of the deal, the Port Authority renamed the H&M “Port Authority Trans-Hudson”, or PATH for short.

To compensate Radio Row business owners for their displacement, the Port Authority gave each business $3,000, without regard to how long the business had been there or how prosperous it was. The Port Authority began purchasing properties in the area for the World Trade Center by March 1965, and demolition of Radio Row began in March 1966. It was completely demolished by the end of the year.

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 whereby 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.



World Trade Center under construction in 1971

In March 1965, the Port Authority began acquiring property at the World Trade Center site. Demolition work began on March 21, 1966, to clear thirteen square blocks of low rise buildings in Radio Row for its construction. Groundbreaking for the construction of the World Trade Center took place on August 5, 1966.

The site of the World Trade Center was located on filled land with the bedrock located 65 feet (20 m) below. 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.[60] The slurry method selected by the 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 the excavation of material from the interior of the site could begin. The 1,200,000 cubic yards (920,000 m3) of excavated material were used (along with other fill and dredge material) to expand the Manhattan shoreline across West Street to form Battery Park City.

In January 1967, the Port Authority awarded $74 million in contracts to various steel suppliers. Construction work began on the North Tower in August 1968, and construction on the South Tower was under way by January 1969. The original Hudson Tubes, which carried PATH trains into Hudson Terminal, remained in service during the construction process until 1971, when a new station opened. The topping out ceremony of 1 WTC (North Tower) took place on December 23, 1970, while 2 WTC’s ceremony (South Tower) occurred on July 19, 1971. Extensive use of prefabricated components helped to speed up the construction process, and the first tenants moved into the North Tower in December 15, 1970, while it was still under construction, while the South Tower began accepting tenants 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 took place on April 4, 1973.

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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.


Major events

February 13, 1975, fire

On February 13, 1975, a three-alarm fire broke out on the 11th floor of the North Tower. It spread to the 9th and 14th floors after igniting telephone cable insulation in a utility shaft that ran vertically between floors. Areas at the furthest extent of the fire were extinguished almost immediately; 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. Fireproofing protected the steel and there was no structural damage to the tower. In addition to fire damage on the 9th through the 14th floors, the water used to extinguish the fire damaged a few of the floors below. At that time, the World Trade Center had no fire sprinkler systems.


February 26, 1993, bombing

Atermath of the 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 in the attacks, some from smoke inhalation. Sheikh Omar Abdel Rahman and four other individuals were later convicted for their involvement in the bombing, while Yousef and Eyad Ismoil were convicted for carrying out 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.

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 pathway 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 were destroyed. A memorial to the victims of the bombing, a reflecting pool, was installed with the names of those who were killed in the blast. It was destroyed following the September 11 attacks. The names of the victims of the 1993 bombing are included in the National September 11 Memorial & Museum.


January 14, 1998, robbery

Looking up at the World Trade Center from Austin J. Tobin Plaza, 1995

In January 1998, Mafia member Ralph Guarino gained maintenance access to the World Trade Center. He arranged a three-man crew for a heist that netted over $2 million from a Brinks delivery to the 11th floor of the North Tower.

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A fireball rises in the immediate aftermath of United Airlines Flight 175 hitting the South Tower during the September 11 attacks.

On September 11, 2001, Islamist terrorists hijacked American Airlines Flight 11 and crashed it into the northern façade of the North Tower  at 8:46:40 a.m.; the aircraft struck between the 93rd and 99th floors. Seventeen minutes later, at 9:03:11 a.m., a second group crashed the similarly hijacked United Airlines Flight 175 into the southern façade of the South Tower, striking it between the 77th and 85th floors. The terrorist organisation Al-Qaeda, led by Osama bin Laden, carried out the attacks in retaliation for certain aspects of American foreign policy, particularly U.S. support of Israel and the presence of U.S. troops in Saudi Arabia. The damage caused to the North Tower by Flight 11 destroyed any means of escape from above the impact zone, trapping 1,344 people. Flight 175 had a much more off-centered impact compared to Flight 11, and a single stairwell was left intact; however, only a few people managed to descend successfully before the tower collapsed. Although the South Tower was struck lower than the North Tower, thus affecting more floors, a smaller number, fewer than 700, were killed instantly or trapped.

At 9:59 a.m., the South Tower collapsed after burning for approximately 56 minutes. The fire caused steel structural elements, already weakened from the plane’s impact, to fail. The North Tower collapsed at 10:28 a.m., after burning for approximately 102 minutes. At 5:20 p.m. on September 11, 2001, 7 World Trade Center began to collapse with the crumbling of the east penthouse; it collapsed completely at 5:21 p.m. owing to uncontrolled fires causing structural failure.


World Trade Center site after 9/11 attacks, seen from above with original building locations outlined in yellow.

The Marriott World Trade Center hotel was destroyed during the collapse of the two towers. The three remaining buildings in the WTC plaza were extensively damaged by debris and were later demolished. The cleanup and recovery process at the World Trade Center site took eight months. The Deutsche Bank Building across Liberty Street from the World Trade Center complex was later condemned because of the uninhabitable toxic conditions inside; it was deconstructed, with work completed in early 2015. The Borough of Manhattan Community College’s Fiterman Hall at 30 West Broadway was also condemned owing to extensive damage, and it was demolished and completely rebuilt.

In the immediate aftermath of the attacks, media reports suggested that tens of thousands might have been killed in the attacks, as over 50,000 people could have been inside the World Trade Center. The National Institute of Standards and Technology (NIST) estimated approximately 17,400 individuals were in the towers at the time of the attacks. Ultimately, 2,753 death certificates (excluding those for hijackers) were filed relating to the 9/11 attacks. 2,192 civilians died in and around the World Trade Center, including employees of Cantor Fitzgerald L.P. (an investment bank on the 101st–105th floors of One World Trade Center), Marsh & McLennan Companies (located immediately below Cantor Fitzgerald on floors 93–101, the location of Flight 11’s impact), and Aon Corporation. In addition to the civilian deaths, 414 sworn personnel were also killed: 340 New York City Fire Department (FDNY) firefighters; 71 law enforcement officers, including 37 members of the Port Authority Police Department (PAPD) and 23 members of the New York City Police Department (NYPD); 2 FDNY paramedics; and 1 FDNY chaplain. Eight EMS personnel from private agencies also died in the attacks. Ten years after the attacks, the remains of only 1,629 victims had been identified. Of all the people who were still in the towers when they collapsed, only 20 were pulled out alive.


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