Trade Center is more than its signature twin towers: it is a complex of
seven buildings on 16-acres, constructed and operated by the Port Authority
of New York and New Jersey (PANYNJ). The towers, One and Two World Trade
Center, rise at the heart of the complex, each climbing more than 100
feet higher than the silver mast of the Empire State Building.
of a world trade facility had been under consideration since the end of
WWII. In the late 1950s the Port Authority took interest in the project
and in 1962 fixed its site on the west side of Lower Manhattan on a superblock
bounded by Vesey, Liberty, Church and West Streets. Architect Minoru Yamasaki
was selected to design the project; architects Emery Roth & Sons handled
production work, and, at the request of Yamasaki, the firm of Worthington,
Skilling, Helle and Jackson served as engineers.
Authority envisioned a project with a total of 10 million square feet
of office space. To achieve this, Yamasaki considered more than a hundred
different building configurations before settling on the concept of twin
towers and three lower-rise structures. Designed to be very tall to maximize
the area of the plaza, the towers were initially to rise to only 80-90
stories. Only later was it decided to construct them as the world's tallest
buildings, following a suggestion said to have originated with the Port
Authority's public relations staff.
and engineers John Skilling and Les Robertson worked closely, and the
relationship between the towersí design and structure is clear. Faced
with the difficulties of building to unprecedented heights, the engineers
employed an innovative structural model: a rigid "hollow tube" of closely
spaced steel columns with floor trusses extending across to a central
core. The columns, finished with a silver-colored aluminum alloy, were
18 3/4" wide and set only 22" apart, making the towers appear from afar
to have no windows at all.
to the engineering design were its core and elevator system. The twin
towers were the first supertall buildings designed without any masonry.
Worried that the intense air pressure created by the buildingsí high speed
elevators might buckle conventional shafts, engineers designed a solution
using a drywall system fixed to the reinforced steel core. For the elevators,
to serve 110 stories with a traditional configuration would have required
half the area of the lower stories be used for shaftways. Otis Elevators
developed an express and local system, whereby passengers would change
at "sky lobbies" on the 44th and 78th floors, halving the number of shaftways.
began in 1966 and cost an estimated $1.5 billion. One World Trade Center
was ready for its first tenants in late 1970, though the upper stories
were not completed until 1972; Two World Trade Center was finished in
1973. Excavation to bedrock 70 feet below produced the material for the
Battery Park City landfill project in the Hudson River. When complete,
the Center met with mixed reviews, but at 1,368 and 1,362 feet and 110
stories each, the twin towers were the world's tallest, and largest, buildings
until the Sears Tower surpassed them both in 1974.