Willis Tower, formerly named Sears Tower, is a 108-story, 1451-foot (442 m) skyscraper in Chicago, Illinois. At the time of its completion in 1974, it was the tallest building in the world, surpassing the World Trade Center towers in New York, and it held this rank for nearly 25 years. The Willis Tower is the tallest building in the United States and the fifth-tallest freestanding structure in the world, as well as the fifth tallest building in the world to the roof.