who was the architect?
Minoru Yamasaki
Construction of the World Trade Center
The Port Authority hired architect Minoru Yamasaki, who came up with the specific idea for twin towers. 
when did construction start on the world trade center March 21, 1965 by whom was it started? David Rockefeller who planned for the structure? Skidmore, Owings and Merrill was it insulated against fire? Yes, sprayed-fire resistant materials (SFRMs) were used to protect some structural steel elements in the towers, including all floor trusses and beams.
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Construction of the World Trade Center [SEP] Introduction
After extensive negotiations, the New Jersey and New York state governments agreed to support the World Trade Center project, which was built at the site of Radio Row in the Lower West Side of Manhattan, New York City. To make the agreement acceptable to New Jersey, the Port Authority agreed to take over the bankrupt Hudson & Manhattan Railroad, which brought commuters from New Jersey to the Lower Manhattan site and, upon the Port Authority's takeover of the railroad, was renamed PATH. The Port Authority hired architect Minoru Yamasaki, who came up with the specific idea for twin towers. The towers were designed as framed tube structures, which provided tenants with open floor plans, uninterrupted by columns or walls.