At the time of their completion, the “Twin Towers” — the original 1 World Trade Center, at 1,368 feet (417 m); and 2 World Trade Center, at 1,362 feet (415 m) — were the tallest buildings in the world. The other buildings in the complex included the Marriott World Trade Center (3 WTC), 4 WTC, 5 WTC, 6 WTC, and 7 WTC. All these buildings were built between 1975 and 1985, with a construction cost of $400 million ($2,300,000,000 in 2014 dollars). The complex was located in New York City’s Financial District and contained 13,400,000 square feet (1,240,000 m2) of office space.
The site of the World Trade Center was located on landfill with the bedrock located 65 feet (20 m) below. To construct the World Trade Center, it was necessary to build a “bathtub” with a slurry wall around the West Street side of the site, to keep water from the Hudson River out. The slurry method selected by Port Authority’s chief engineer, John M. Kyle, Jr., involved digging a trench, and as excavation proceeded, filling the space with a “slurry” mixture composed of bentonite and water, which plugged holes and kept groundwater out. When the trench was dug out, a steel cage was inserted and concrete was poured in, forcing the “slurry” out. It took fourteen months for the slurry wall to be completed. It was necessary before excavation of material from the interior of the site could begin. The 1,200,000 cubic yards (920,000 m3) of material excavated were used (along with other fill and dredge material) to expand the Manhattan shoreline across West Street to form Battery Park City.
In January 1967, the Port Authority awarded $74 million in contracts to various steel suppliers, and Karl Koch was hired to erect the steel. Tishman Realty & Construction was hired in February 1967 to oversee construction of the project. Construction work began on the North Tower in August 1968; construction on the South Tower was underway by January 1969. The original Hudson Tubes, carrying PATH trains into Hudson Terminal, remained in service as elevated tunnels during the construction process until 1971 when a new PATH station opened.
The topping out ceremony of 1 WTC (North Tower) took place on December 23rd, 1970, while 2 WTC’s ceremony (South Tower) occurred later on July 19th, 1971.The first tenants moved into the North Tower on December 15, 1970; the South Tower accepted tenants in January 1972. When the World Trade Center twin towers were completed, the total costs to the Port Authority had reached $900 million. The ribbon cutting ceremony was on April 4, 1973.
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 1970’s. The 47-story 7 World Trade Center building was added in the 1980’s, to the north of the main complex. Altogether, the main World Trade Center complex occupied a 16-acre (65,000 m2) superblock.
Plans to build the World Trade Center were controversial. The site for the World Trade Center was the location of Radio Row, home to hundreds of commercial and industrial tenants, property owners, small businesses, and approximately 100 residents, many of whom fiercely resisted forced relocation. A group of small businesses affected filed an injunction challenging the Port Authority’s power of eminent domain. The case made its way through the court system to the United States Supreme Court; the Court refused to accept the case