who made the twin towers

The Twin Towers of the original World Trade Center were designed by architect Minoru Yamasaki. The structural engineering firm Worthington, Skilling, Helle & Jackson implemented Yamasaki's design, creating the framed tube structural system used in the towers. The general contractor for the project was Tishman Realty & Construction Company. The project was developed by the Port Authority of New York and New Jersey, led by director Guy F. Tozzoli and Chief Engineer Rino M. Monti. Construction on the North Tower began in August 1968 and the South Tower followed in early 1969, with the North Tower completed in December 1970 and the South Tower in July 1971. The design incorporated innovative engineering techniques by engineer Leslie E. Robertson to free the floors of unnecessary columns and allow open floor plans.