when were the twin towers built

The Twin Towers of the World Trade Center were constructed primarily between 1968 and 1973. Construction began with the North Tower in August 1968 and the South Tower in January 1969. The North Tower was topped out in December 1970, and the South Tower followed in July 1971. The official ribbon-cutting and opening ceremony for the Twin Towers took place on April 4, 1973. Tenants began moving into the North Tower as early as December 1970, before the completion of the building, and into the South Tower starting January 1972.