Construction Of The World Trade Center

On September 20, 1962, the Port Authority announced the selection of Minoru Yamasaki as lead architect and Emery Roth & Sons as associate architects. Yamasaki devised the plan to incorporate twin towers; Yamasaki's original plan called for the towers to be 80 stories tall. To meet the Port Authority's requirement for 10,000,000 square feet (930,000 m2)) of office space, the buildings would each have to be 110 stories tall.
A major limiting factor in building height is the issue of elevators; the taller the building, the more elevators are needed to service the building, requiring more space-consuming elevator banks. Yamasaki and the engineers decided to use a new system with two "sky lobbies"—floors where people could switch from a large-capacity express elevator to a local elevator that goes to each floor in a section. This allowed the design to stack local elevators 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, increasing the amount of usable space on each floor from 62 to 75 percent by reducing the number of elevator shafts. 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 express stations where both express and local trains stop and local stations where only local trains stop.
Yamasaki's design for the World Trade Center, unveiled to the public on January 18, 1964, called for a square plan approximately 208 feet (63 m) in dimension on each side. The buildings were designed with narrow office windows 18 inches (46 cm) wide, which reflected Yamasaki's fear of heights as well as his desire to make building occupants feel secure. Yamasaki's design included building facades sheathed in aluminum-alloy. The World Trade Center was one of the most-striking American implementations of the architectural ethic of Le Corbusier, and it was the seminal expression of Yamasaki's gothic modernist tendencies.
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.