High Quality Content by WIKIPEDIA articles! Willis Tower (formerly named and still commonly referred to as Sears Tower) is a 108-story, 1,451-foot (442 m) skyscraper in Chicago, Illinois. At the time of its completion in 1973, 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 seventh-tallest freestanding structure in the world. The skyscraper is one of the most popular tourist destinations in Chicago, and over one million people visit its observation deck each year.