complex of several buildings around a central plaza in New York City that in 2001 was the site of the deadliest terrorist (terrorism) attack in American history. (See September 11 attacks.) The complex—located at the southwestern tip of Manhattan, near the shore of the Hudson River and a few blocks northwest of Wall Street—was built by the Port Authority of New York and New Jersey as a central facility for businesses and government agencies involved in international trade. Until the 2001 attack, it was notable for its huge twin towers, each of which had 110 stories, that formed a distinctive feature of the New York skyline. The roof of One World Trade Center reached to 1,368 feet (417 metres), and Two World Trade Center was 1,362 feet (415 metres) tall. Designed by architect Minoru Yamasaki (Yamasaki, Minoru) and officially opened in 1972, the towers were the world's tallest buildings until surpassed in 1973 by the Sears Tower in Chicago. (See Researcher's Note: Heights of Buildings.) Each of the twin towers had 97 passenger elevators, 21,800 windows, and roughly an acre (0.4 hectare) of rentable space per floor. An observation deck was situated on the 107th floor of the south tower (Two World Trade Center), and a television-broadcasting mast 360 feet (110 metres) high was attached to the north tower (One World Trade Center).

Workers spent nearly a year removing the debris and recovering bodies from the ruins at the World Trade Center complex site, and an intense national discussion ensued on how best to rebuild it. Two design competitions were launched, beginning in the summer of 2002: one to replace the fallen towers and the other for a memorial to the victims of both the 1993 and 2001 attacks. A winning building design was announced in early 2003. Named “Freedom Tower,” it was planned to rise to a height of 1,776 feet (541 metres). The tower's design underwent further modification (though the height remained the same), which was made public in June 2005 (with further refinements appearing a year later). The winning design for the memorial was announced in January 2004; the plans for it were also revised (unveiled in June 2006). Called “Reflecting Absence,” it was to consist of two pools (one in each tower's footprint void) surrounded by trees and by walls containing the names of the victims.