World Trade Center former building complex in lower Manhattan, New York City, consisting of seven buildings and a shopping concourse on a 16-acre (6.5-hectare) site; it was destroyed by a terrorist attack on Sept. 11, 2001. Prior to its destruction, the World Trade Center had been the world's largest commercial complex, home to many businesses, government agencies, and international trade organizations. Most prominent among its structures were the 110-story rectangular twin towers, one rising to 1,362 ft (415 m) and the other to 1,368 ft (417 m), with floors roughly an acre in size. Designed by Minoru Yamasaki and Emery Roth, the towers and concourse portion of the center were completed in 1973 at a cost of some $750 million. For a brief period (until the completion of the Sears Tower in Chicago in 1974), the World Trade towers were the tallest buildings in the world. They remained the largest structures on the Eastern Seaboard of the United States, an internationally known landmark and tourist attraction rising high above the skyline of lower Manhattan.

In 1993 a terrorist car-bomb explosion damaged portions of the complex, killing six people and causing more than $300 million in damage. Sheik Omar Abdel Rahman and nine other Islamic extremists were convicted of conspiracy and other charges related to the bombing in 1993, and the so-called mastermind, Ramzi Yousef, was convicted in 1998. On Sept. 11, 2001, a second terrorist attack, in which two hijacked commercial jetliners were crashed into the towers, ignited huge, intense fires in the upper stories of both buildings, weakening them and leading to their collapse. Other structures in the complex were completely or partially destroyed as a result, and many surrounding buildings were severely damaged. More than 2,700 people, including the passengers and crew of the airliners and several hundred emergency personnel responding to the initial fires, lost their lives; more than 7,000 people were injured.

The enormity of the events of Sept. 11 (see also 9/11 ), which also involved a similar attack with a hijacked jetliner on the Pentagon in Washington, D.C., and the crash in W Pennsylvania of a fourth hijacked plane, galvanized national feeling in the United States, where many watched the events unfold on television. In the aftermath of the worst terrorist attack in history, President George W. Bush announced a war on terrorism , and many nations pledged their support. Al Qaeda, headed by Osama bin Laden , was identified by U.S. authorities as being behind the attacks, and the United States subsequently began military operations in Afghanistan, where bin Laden was based and where the government was closely allied with him.

In Dec., 2001, Zacarias Moussaoui, a Frenchman of Moroccan descent who had been arrested (Aug., 2001) on immigration violations in Minnesota, was indicted on charges that he was part of the conspiracy responsible for the September attacks. He pleaded guilty in 2005 to being part of a conspiracy to attack the White House in a similar manner but denied being part of either Sept. 11 attack, and was given a life sentence in 2006.

The alleged mastermind of the plot was Khalid Sheikh Mohammed, a Kuwaiti of Pakistani parentage who had become a high-ranking member of Al Qaeda. He was captured in Pakistan in 2003, held by the United States at an undisclosed location, and transferred to Guantánamo Bay in 2006. According to a censored transcript of a closed-door hearing in 2007, he admitted to organizing and supervising the execution of the attacks of Sept. 11, but the government also later revealed that he had been subjected to waterboarding, which is generally regarded as a form of torture. In Feb., 2008, the Pentagon announced that a military tribunal would try Mohammed and five others held at Guantánamo on conspiracy and other charges relating to the attacks.

In the aftermath of the center's destruction, many competing interests—the city and state of New York, the owners of the site, the buildings' developer, survivors of the attack and families and friends of those killed, and others—advocated a variety of approaches to rebuilding the site. After a lengthy design competition, a preliminary master construction plan for the site, by Daniel Libeskind , was approved in 2003. The design has since been much modified, and a new overall plan was unveiled in 2006.

Embracing the footprints where the towers once stood, a street-level memorial plaza is planned, with two sunken pools fed by waterfalls; the names of those who died as a result of the attack will be displayed in the plaza, which will also include a World Trade Center Museum. Surrounding the memorial, will be a group of office towers that rise in height toward the the "Freedom Tower" (Tower 1), designed by the American architect David M. Childs of Skidmore, Owings and Merrill . Tower 2 is being designed by England's Lord Norman Foster , Tower 3 by another English architect, Lord Richard Rogers, and Tower 4 by Japan's Fumihiko Maki. The complex will also include a transportation hub by Spain's Santiago Calatrava and a performing arts center to be created by Frank Gehry .

Bibliography: See studies by E. Darton (1999), A. K. Gillespie (1999), W. Langewiesche (2002), and J. Glanz and E. Lipton (2003).

World Trade Center, 1993 Terrorist Attack

█ JUDSON KNIGHT

The World Trade Center (WTC) bombing of 1993 has long since been overshadowed by the attack that brought the twin towers down on September 11, 2001. Yet, at the time it occurred, the attack loomed as large on the American landscape as the towers themselves once did on the Manhattan skyline. The attack killed six people and injured more than a thousand, the first casualties from foreign terrorists on U.S. soil. American authorities identified at least eight perpetrators, but questions remain as to the ultimate cause of the attack.

The attack and its aftermath. At 12:18 p.m. on Friday, February 26, 1993, an explosion rocked the second level of the parking basement beneath Trade Tower One. The explosive material, as investigators would later determine, was somewhere between 1,200 and 1,500 pounds (544–680 kg) of urea nitrate, a homemade fertilizer-based explosive.

The blast ripped open a crater 150 feet (46 m) in diameter and five floors deep, rupturing sewer and water mains and cutting off electricity. Over the hours that followed, more than 50,000 people were evacuated from the Trade Center complex. A stunned nation soon grasped a fact larger than the incident itself: foreign-sponsored terrorism—which had long plagued Western Europe and parts of the Middle East, Africa, and Asia—had come to the United States.

Investigation and cleanup begins. The first analysis team to arrive came from the Federal Bureau of Investigation (FBI), who soon brought in two examiners from the FBI Laboratory Explosives Unit. Over the week that followed, a team of more than 300 law-enforcement officers from various agencies throughout the country would sift through some 2,500 cubic yards (1,911 cubic meters) of debris weighing more than 6,800 tons (6,909 tonnes).

At the same time that this forensic investigation began, government authorities rushed to protect against physical, chemical, and biological hazards associated with the blast. The explosion had exposed raw sewage, asbestos, mineral wool, acid, and fumes from automobiles. Meanwhile, small electrical fires burned, and pieces of concrete and sharp metal hung threateningly from distended beams.

On Saturday, authorities installed seismographic equipment, cleared the area, and conducted a test run of an empty subway train. The results showed that with a few adjustments, the area could be rendered safe for the operation of the Port Authority Transportation system (PATH) on Monday, thus preventing a virtual shutdown of lower Manhattan. The Environmental Protection Agency and the Occupational Safety and Health Administration began taking steps to clean up biological and chemical debris.

Tracking the killers. Meanwhile, the forensic investigation expanded, with two chemists each from the FBI, ATF (Bureau of Alcohol, Tobacco, and Firearms), and New York Police Department collecting and studying residue from the blast area. In the course of this work, investigators found a key piece of evidence: a 300-pound (136-kg) fragment of a vehicle that, based on the damage it had sustained, must have been at the very epicenter of the blast. Sewage contamination had rendered it unusable for residue analysis, but it bore something much better: a vehicle identification number (VIN).

This was not to be the first fortunate break for investigators. Authorities traced the vehicle to a Ryder truck rental facility in Jersey City, New Jersey, from which it had been reported stolen. On Monday, while FBI special agents were at the Jersey City facility to speak with personnel there, the Ryder clerk received a call from a man identified as Mohamed Salemeh. The latter demanded the return of

his $400 deposit for the van in question, and the Ryder clerk arranged for him to return and collect the deposit on March 4, 1993. When Salemeh arrived, he was arrested.

A search of Salemeh's belongings led investigators to Nidal Ayad, a chemist working for the Allied Signal Corporation in New Jersey. Toll records and receipts helped lead to a safe house in Jersey City, New Jersey, where authorities found traces of nitroglycerine and urea nitrate. They also uncovered evidence that Salemeh and Ayad had obtained three tanks of compressed hydrogen gas, and in the course of searching a storage room rented by Salemeh, investigators found large caches of urea, sulfuric acid, and other chemicals used in making a bomb. On March 3, the New York Times received a letter claiming responsibility for the bombing, and subsequent investigation of DNA samples matched Ayad with the saliva on the envelope flap.

Conviction—and continuing questions. The trail of investigation would eventually lead to Ramzi Yousef, who authorities believe was in the van that delivered the explosives to the WTC. With him was Eyad Ismoil. Also implicated in the bombing, along with Salemeh and Ayad, were Ahmad Ajaj, Mahmoud Abouhalima, and Abdul Rahman Yasin. On March 4, 1994, a jury found Salemeh, Ajaj, Abouhalima, and Ayad guilty on 38 counts, including murder and conspiracy, and the judge handed down multiple life sentences.

Yousef fled the country, and engaged in other terror plots before he was captured and brought to the United States from Pakistan in February 1995. He was sentenced to life plus 240 years. As of 2003, Yasin had not been captured, and was believed to be in Iraq. In October 1995, Sheikh Omar Abdel Rahman, a blind Egyptian cleric who taught at mosques in Brooklyn and New Jersey, was sentenced to life imprisonment for masterminding the attack. But some observers wonder whether the roots of the 1993 WTC attack run much deeper.

The fact that Yousef is the nephew of Khalid Sheikh Mohammed, a top figure in al-Qaeda, suggests a strong connection between the 1993 conspirators and the group who ultimately brought down the towers eight years later. After the September 2001, attack, it was the opinion of many investigators and analysts inside President George W. Bush's administration, that the perpetrators of that attack had a state sponsor—Iraq. A number of details, including the fact that Yousef was traveling on an Iraqi passport, as well as the date of the 1993 attack—the second anniversary of the U.S. liberation of Kuwait in the Persian Gulf War—furthered suspicions of Iraqi involvement in the 1993 incident. Mohammed was later involved in masterminding the terrorist attacks on the World Trade Center in 2001, and was arrested in Rawalpindi, Pakistan on March 1, 2003.

█ FURTHER READING:

BOOKS:

Dwyer, Jim. Two Seconds Under the World: Terror Comes to America. New York: Crown Publishers, 1994.

Gillespie, Angus K. Twin Towers: The Life of New York City's World Trade Center. New Brunswick, NJ: Rutgers University Press, 1999.

Juergensmeyer, Mark. Terror in the Mind of God: The Global Rise of Religious Violence. Berkeley: University of California Press, 2000.

Mylroie, Laurie. Study of Revenge: The First World Trade Center Attack and Saddam Hussein's War against America. Washington, D.C.: AEI Press, 2001.

Reeve, Simon. The New Jackals: Ramzi Yousef, Osama bin Laden, and the Future of Terrorism. Boston: Northeastern University Press, 1999.

ELECTRONIC:

Hirschkorn, Phil. Top Terrorist Convictions Upheld. Cable News Network. <http://www.cnn.com/2003/LAW/04/04/terrorism.yousef/> (April 7, 2003).

SEE ALSO

Bomb Damage, Forensic Assessment
Clinton Administration (1993–2001), United States National Security Policy
United States, Counter-terrorism Policy
Terrorist and Para-State Organizations
World Trade Center, 2001 Terrorist Attack

World Trade Center, 2001 Terrorist Attack

█ JUDSON KNIGHT

At 8:46 a.m. on September 11, 2001, American Airlines Flight 11, hijacked from Boston's Logan Airport with 92 people on board, crashed into the upper floors of the World Trade Center north tower in lower Manhattan, New York. Seventeen minutes later, United Airlines Flight 175, also hijacked from Logan and with 65 people on board, crashed into the south tower. By this time, virtually the entire nation had tuned in to witness the after-effects on television of what at first seemed a terrible accident, but was quickly revealed as a terrorist attack. Over the course of the next 85 minutes, the south tower collapsed, followed by the collapse of the north tower. The incident, in which nearly 3,000 people died, ranks as by far the worst case of mass murder in U.S. history, the worst building disaster in human history, and the largest terrorist incident in the history of the western world.

The Towers and their Environment

Designed by architect Minoru Yamasaki—who, ironically, had a fear of heights—and engineered by Leslie Robertson and John Skilling, the 110-story towers soared 1,360 feet (415 m) above an open plaza, which made them the world's tallest buildings at the time of their completion in 1973. Whereas the Empire State Building and other older skyscrapers drew support from an interior grid of steel girders, support for the trade towers came from the exterior and the inner core. Horizontal floor trusses joined the perimeter support structure to the central area, which the engineers envisioned as a great "tube" running through the building and containing not only its support structure, but also its utilities such as elevators. This design had two advantages; it made the buildings extremely stable—not prone to swaying in high winds as the Empire State did—and it left much of the interior available as rentable space.

To support such a structure required a strong foundation, and in this regard, the location in lower Manhattan was not a promising one. Bedrock lay between 55 and 80 feet (17–24 m) below street level, and to get to it, construction crews had to deal with another engineering challenge: flooding from the nearby Hudson River. In order to dig without flooding the site, they dug narrow trenches to the bedrock, and as they went, they pumped in a slurry of water and bentonite, a type of clay that expanded to prevent groundwater from flowing in. The slurry trench method made it possible to build a watertight framework for the excavation of the foundation structure, nicknamed "the bathtub."

Excavation began in 1966, and yielded such a quantity of fill that it was used to reclaim 28 acres (11.3 hectares) from the Hudson to form Battery Park City. In addition to supports, in the area underneath the buildings would be seven stories of parking decks, stores, and subway lines. The erection of the buildings themselves, which took more than five years, was a massive feat of both construction and logistics, involving 200,000 tons (181,437) of steel, each major piece of which was marked with an identification number. Over the years of building, many businesses moved in long before the towers were officially completed.

28 years in the towers' lives. On April 4, 1973, the World Trade Center officially opened for business. Though the towers were by far the most notable aspect of the project, they were just two of seven buildings in the entire complex. Built at a cost of $1 billion, the towers functioned as virtual cities unto themselves, with some 500 businesses, including banks and their offices, law firms, brokerage houses, television stations, charitable organizations, airlines, and government offices. Supporting these functions and the 50,000 employees who filled them were numerous restaurants—most notable of which was "Windows on the World" at the top of the North Tower—as well as other services, including nine chapels of different faiths.

By the 1980s, New Yorkers had become accustomed to the trade towers, which punctuated the skyline as the ultimate symbol of American commerce. Then, in February 1993, just months before the towers turned 20, the towers became the target for a bombing by Islamist terrorists operating a van filled with explosives. In this, the first terrorist attack, six people were killed, but the structural integrity of the towers themselves was not threatened.

September 11 and Its Aftermath

Because of the 1993 attack, many Americans who witnessed the events of September 11, 2001, quickly realized that the buildings had once again become the target for terrorists. When Flight 11 crashed into the North Tower of the World Trade Center at 8:46 a.m., smoke and flames began to gush from the upper stories, and workers began to evacuate the lower floors. Some, however, chose to remain at their desks. For workers on the floors above the impact area, there was no choice but to remain in place.

For 17 minutes, it was possible to assume that what had happened to the North Tower was an accident; then, Flight 175 smashed into the South Tower. Once again, smoke and flames erupted from the heights of the building, and tenants down below began a slow, but steady evacuation while others—many with no choice—stayed where they were.

By 9:59 a.m., millions of Americans had turned on their television sets to watch live reports from the site. Thus, there was a vast audience to experience what happened next, an event that would be etched upon the consciousness of an entire nation. With little warning, the South Tower, succumbing to the stress caused by the fire, began to crash from the top down, creating a vast cloud of dust and ash above and filling the streets below with noise and heat and terror.

By 10:28 a.m., the North Tower began to implode, once again crashing downward from the top, and the area around what had once been the World Trade Center became smoke, ash, and dust. The other five buildings in the former World Trade Center complex, including the Marriott Hotel, the Commodities Exchange, Dean Witter, the U.S. Customs House, and 7 World Trade Center, were destroyed as well. The last of these caught fire, and collapsed that night.

Rescue, cleanup, and the death toll. In the next days and weeks, some 1,500 firemen, search and rescue workers, ironworkers, engineers, heavy equipment operators, and others labored at the site where the towers had stood, a place now known variously as "Ground Zero" or "the Hole." In the shock and horror that followed the attacks, among the few bright spots were the many tales of heroism told by people who owed their lives to police, fire, and medical personnel.

That heroism continued in the weeks of the cleanup, as rescue workers sifted through piles of wreckage. The purpose of their job was manifold. Not only were they cleaning the site, but they were looking for evidence, and—most poignantly—for any signs of the dead.

At first, rescuers had hoped to find survivors trapped under the rubble and trauma centers at local hospitals braced to treat mass casualties, but those hopes faded quickly, and the cleanup work involved sifting through materials that included physical traces of the building's former inhabitants. Not only was the cleanup work grisly, it was also dangerous: rather than working on solid ground, the rescuers had to set up their cranes and other equipment on top of debris piled several hundred feet above the buildings' foundations.

The numbers of the dead would emerge slowly, and had yet to be fully authenticated even two years later. Although the dead numbered 2801, it was estimated that at the early morning hour, almost 7000 of the 50,000 people who worked in the buildings were in their offices at the time of the attacks. Although the span of time between the attacks and the collapse of the buildings was little more than an hour, it had been enough for those who were able to do so to evacuate via stairwells.

Structural explanations. In late 2001, a team of investigators that included representatives of the American Society of Civil Engineers and the Federal Emergency Management Agency (FEMA) commenced a study on the structural collapse of the towers, the details of which they made public in April 2002. In August 2002, the National Institute of Standards and Technology (NIST) began its own study, scheduled to last two years.

The first team concluded that it was not the impact, but the heat from the burning jet fuel, that heated the temperature of the buildings' steel support structures up to 800°C (1472°F), causing them to buckle and the floors to collapse downward. (Both jets were bound for Los Angeles and had almost a full complement of fuel on board.) On the other hand, the impact did have the effect of knocking out support columns in the building's interior, which may have weakened the structure. The initial crash neutralized sprinkler systems, allowing spread of the fire, which was fed by caches of paper and other flammable materials in offices.

Almost all sources, including government officials, architects, and engineers, agreed on key elements of the building damage. First, it would have been virtually impossible to prevent the destruction of the buildings by aircraft used in the way they were on September 11 as guided missiles. Second, the structural integrity of the buildings that allowed the towers to stand for over an hour after the impacts enabled thousands of people to evacuate. Finally, it was evident that the era of the extremely tall skyscraper was in question. Due to high costs, the construction of very tall buildings had been on the decline in the United States for many years, and the events of 9/11 sealed the fate of some mega-skyscraper projects.

The perpetrators. Federal authorities, using financial records and other materials, had long since identified the al-Qaeda terror network as the perpetrators of the attack. Al-Qaeda was not a new name: it and its leader, Osama bin Laden, had been linked with the August 1998 bombings at U.S. embassies in Africa, and with the bombing of the USS Cole in Yemen in 2000.

Al-Qaeda had strong links to the Taliban regime in Afghanistan, which gave them asylum. Officials in the administration of President George W. Bush, as well as some observers outside the administration, also held that there were substantive links between al-Qaeda, the terrorists who carried out the 1993 bombing, and the government of Iraq. (In fact, Ramzi Youssef, one of the ring leaders in 1993, was nephew to Khalid Sheikh Mohammed, a top al-Qaeda operative, and considerable evidence—including Youssef's Iraqi passport—linked them to Iraq.) The U.S. military actions against Afghanistan in 2001–2002, and Iraq in 2003, were a response to the 2001 terrorist attacks, whose most potent images revolved around the collapse of the World Trade Center towers.

█ FURTHER READING:

BOOKS:

Halberstam, David. New York September 11. New York: Power House Books, 2001.

Hoge, James F., and Gideon Rose. How Did This Happen?: Terrorism and the New War. New York: PublicAffairs, 2001.

One Nation: America Remembers September 11, 2001. Boston: Little, Brown, 2001.

Smith, Dennis. Report from Ground Zero: The Story of the Rescue Efforts at the World Trade Center. New York: Viking, 2002.

ELECTRONIC:

Day One—The Attack. Los Angeles Times. <http://www.latimes.com/news/nationworld/nation/la-dayonegraphics.story> (April 22, 2003).

September 11, 2001. How Stuff Works. <http://www.howstuffworks.com/sept-eleven3.htm> (April 22, 2003).

September 11 Archive. <http://september11.archive.org/> (April 22, 2003).

SEE ALSO

Enduring Freedom, Operation
FEMA (United States Federal Emergency Management Agency)
Iraqi Freedom, Operation (2003 War against Iraq)
Kenya, Bombing of United States Embassy
NIST (United States National Institute of Standards and Technology)
Patriot Act, United States
Persian Gulf War
September 11 Terrorist Attacks on the United States
Terrorist and Para-State Organizations
United States, Counter-terrorism Policy
USS Cole,
World Trade Center, 1993 Terrorist Attack