when were the twin towers built before 911
World Trade Center (1973–2001) In January 1967, the Port Authority awarded $74 million in contracts to various steel suppliers.[56] Construction work began on the North Tower in August 1968, and construction on the South Tower was under way by January 1969.[57] The original Hudson Tubes, which carried PATH trains into Hudson Terminal, remained in service during the construction process until 1971, when a new station opened.[58] The topping out ceremony of 1 WTC (North Tower) took place on December 23, 1970, while 2 WTC's ceremony (South Tower) occurred later on July 19, 1971.[57] The first tenants moved into the North Tower on December 15, 1970,[1] while the South Tower started accepting tenants in January 1972.[59] When the World Trade Center twin towers were completed, the total costs to the Port Authority had reached $900 million.[60] The ribbon cutting ceremony was on April 4, 1973.[61]