Now the UPMC headquarters. The U.S. Steel Tower, also known as the Steel Building, or USX Tower, is a 64-story skyscraper at 600 Grant Street in downtown Pittsburgh, Pennsylvania. The interior has 2,300,000 sq ft (210,000 m2) of leasable space. At 256.3 m (841 ft) tall, it is the tallest building in Pittsburgh. It held its opening dedication on September 30, 1971.