World Trade Center

The story of the World Trade Center, especially the buildings known as the "Twin Towers," is a story of achievement and tragedy. The 16-acre site, comprised of two towering buildings and a surrounding plaza along with five other buildings, was a landmark of Lower Manhattan and a soaring presence in the New York City skyline before its destruction in the September 11, 2001, terrorist attacks. Even though the famous original buildings are gone, few other silhouettes remain as recognizable.

The sites of the seven original World Trade Center buildings were redeveloped following the terrorist attacks. A memorial to the victims of the attacks was constructed, along with a museum. New buildings were also erected, most prominently the One World Trade Center tower, originally known as the Freedom Tower, which became the tallest building in North America upon completion in 2014.

Design and Construction

The original World Trade Center buildings were conceived as the result of a massive urban renewal project in Lower Manhattan sponsored by the Port Authority of New York and New Jersey. Architect Minoru Yamasaki was chosen to head the project, and Leslie E. Robertson was the structural engineer who designed the towers' interiors. The project had its critics, since it required the demolition of over one hundred buildings in the area, and caused a dramatic shift in traffic patterns. Many New Yorkers criticized the "Lego-like" design of the towers.

To achieve maximum interior space as well as the towers' then-world-record height of 110 stories, the twin buildings were designed as tubes. Since nearly half of each building's weight was carried by an exoskeleton, or perimeter, of columns and steel plates, few interior columns were needed, creating wide open spaces on each floor.

The closely spaced steel columns and beams that formed the outer walls were faced with aluminum and steel. The steel tube acted as an internal core that allowed the flexible buildings to withstand wind loads, which could cause the towers to sway as much as three feet from true center in strong winds. Web-like bar-joist trusses held up the concrete floors and provided lateral support to the exterior columns to keep them from buckling.

Buildings so large and high have to withstand not only enormous winds but also settlement loads. The towers were built on six acres of landfill, which engineers stabilized by extending the foundation of each tower more than 70 feet below ground level to solid bedrock. The excavation produced the fill material for the Battery Park City landfill project in the Hudson River. The World Trade Center complex was officially opened in April 1973.

Features and Services

The towers' design incorporated other unique features. The Trade Center was a transportation hub with two direct connections to rail transportation. Both PATH (Port Authority Trans Hudson) trains from New Jersey and the MTA (Metropolitan Transit Authority) subway had stops under the twin towers. The Trade Center also provided open space in Lower Manhattan, a valuable commodity in an urban setting. Yamasaki left five acres open in his design for an outdoor plaza, describing it as "an oasis . . . where people can spend a few moments to relieve the tensions and monotonies of the usual working day".

Each tower was served by over 100 freight and passenger elevators, which serviced the approximately 50,000 people who worked at the World Trade Center. In addition to the 500 tenants who rented office space in the towers, thousands of people visited each day for business, entertainment, or shopping. Popular attractions included the Windows on the World restaurant, and the two observation decks at Two World Trade Center, which provided scenic views from more than 1,000 feet above street level.

Tower One, the North Tower, was completed in 1972 and Tower Two, the South Tower, was completed the following year. At 110 stories each, Tower One measured 1,368 feet and Tower Two, 1,362 feet. The twin towers were the two tallest buildings in the world until 1975, when the Sears Tower (later renamed the Willis Tower) in Chicago captured the title and held it until 1998, when it was usurped by Malaysia's 1,483-foot-tall Petronas Towers. The buildings were privatized by the Port Authority in 1998, and leased for management by a private company.

Terrorism

The immense size and iconic status of the World Trade Center and its location in the heart of the US financial industry made it the target of not only critics of perceived American capitalist excess, but also of terrorists bent on attacking the United States. One World Trade Center was the site of a terrorist bombing on February 26, 1993. A truck bomb loaded with 1,100 pounds of explosives exploded in the underground parking garage, killing six people and injuring more than 1,000. The attack was carried out by individuals linked to the al-Qaeda terrorist organization.

Eight years later, on September 11, 2001, the towers were struck again. In a coordinated effort, al-Qaeda terrorists attacked both the towers of the World Trade Center and the Pentagon in Washington, DC, with hijacked passenger jets. A fourth hijacked jet crashed in Pennsylvania.

Destruction

The chronology of the last day of the towers began at approximately 8:45 AM, when a hijacked jet, American Airlines Flight 11 flying from Boston, Massachusetts, crashed into the North Tower of the World Trade Center. The top floors of the building around the gaping hole were set ablaze. Only fifteen minutes later, shortly after 9:00 AM, a second hijacked airliner, United Airlines Flight 175, also flying from Boston, crashed into the South Tower. The explosion also ignited a raging fire in that tower.

The fires weakened the infrastructure of the buildings, collapsing the upper floors. The collapse created too much load for the lower floors to bear, and by 10:05 AM, the South Tower of the World Trade Center, the second tower hit, collapsed. At 10:28 AM, the North Tower collapsed.

Ironically, in the 1970s, engineer Robertson had calculated that the buildings could withstand the impact of being struck by an airplane, but no one could have anticipated the devastating effect of a direct hit with a plane fully loaded with fuel, and the ensuing firestorm that weakened the structures.

Ground Zero and Rebuilding

The rescue efforts and excavation of what became known as Ground Zero lasted for weeks. Most people who were killed on September 11, 2001, worked on the higher floors in the towers, above where the hijacked planes hit, or were still in the towers when they collapsed. Many rescue workers who entered the towers after the strikes were also killed. After a lengthy victim identification process, the confirmed death toll eventually reached 2,977 for all the 9/11 attacks, with the great majority at the World Trade Center site.

The Lower Manhattan Development Corporation, established by former New York Governor George Pataki, oversaw the rebuilding of Ground Zero, which includes a memorial, public areas, and other business and cultural space. After an open design competition, the group chose architect Daniel Libeskind's master plan for rebuilding the 16-acre site in February 2003. In 2004, Michael Arad and Peter Walker's memorial design, called Reflecting Absence, was chosen for the footprint of the Twin Towers.

Though not all seven of the original World Trade Center buildings were completely destroyed in the attacks, they were all damaged and so were demolished to be rebuilt. The first new building to open was 7 World Trade Center, in May 2006. The rebuilding process at the main World Trade Center site began in April 2006. Several delays and design alterations occurred over the next several years, and there was significant controversy surrounding the appropriate way to commemorate the tragedy. Construction of the National September 11 Memorial was finished in 2011, with Reflecting Absence focused around pools of water where the towers once stood. The National September 11 Museum encountered further delays but finally opened in 2014.

One World Trade Center, a 1,776–foot skyscraper originally called the Freedom Tower, was completed later in 2014, becoming the most prominent new building on the site and the tallest building in the United States. The permanent new PATH subway station and associated facilities, known as the World Trade Center Transportation Hub, opened in 2016. Several other buildings and facilities, including other skyscrapers and a performing arts center, were also part of the site's master plan. In addition to the opening of the elevated green space Liberty Park and a shopping mall in 2016, the years 2022 and 2023 saw the reconstruction and reopening of the St. Nicholas Greek Orthodox Church as well as the opening of the newly constructed Perelman Performing Arts Center, respectively.

Bibliography

Dupré, Judith. One World Trade Center: Biography of the Building. Little, Brown, and Company, 2016.

Haerens, Margaret, editor. Rebuilding the World Trade Center. Greenhaven Press, 2012.

"World Trade Center." History, 18 June 2024, www.history.com/topics/world-trade-center. Accessed 31 Dec. 2024.

"World Trade Center: History." Port Authority of New York and New Jersey, www.officialworldtradecenter.com/en/local/learn-about-wtc/history.html#origins. Accessed 31 Dec. 2024.

"World Trade Center History." 9/11 Memorial and Museum, www.911memorial.org/world-trade-center-history. Accessed 31 Dec. 2024.

"World Trade Center Timeline of History." World Trade Center, Silverstein Properties, www.wtc.com/about/history. Accessed 31 Dec. 2024.