High Quality Content by WIKIPEDIA articles! U.S. Steel Tower, also known as the Steel Building (formerly USX Tower), is the tallest skyscraper in Pittsburgh, the fourth tallest building in Pennsylvania, and the 37th tallest in the United States. Completed in 1970, the tower has 64 floors to 841 ft (256 m) and has 2,300,000 sq ft (210,000 m2) of leasable space. Its original name was the U.S. Steel Building for many years before it was changed to USX Tower in 1988. The name was finally changed back to the U.S. Steel Tower in January 2002 to reflect U.S. Steel`s new corporate identity (USX was the 1990s combined oil/energy/steel conglomerate). Although no longer the owner of the building, U.S. Steel is one of the largest tenants, occupying more than a 500,000 sq ft (46,000 m2) of office space. The building is located at 600 Grant Street, ZIP code 15219.