Willis Tower, in Chicago, is one of the tallest buildings in the United States. Until 1998, it ranked as the tallest building in the world. Formerly named the Sears Tower, the building has 110 stories, reaching 1,450 feet (442 meters) high. Twin antenna towers on top of the Willis Tower bring the total height to 1,707 feet (520 meters).
The Willis Tower stands on South Wacker Drive between Adams Street and Jackson Boulevard. The building consists primarily of business offices and some retail stores. An observatory on the 103rd floor called the Skydeck is open to the public. On a clear day, visitors can see four states—Illinois, Indiana, Michigan, and Wisconsin.
The Willis Tower has a black exterior made of aluminum and glass. The inside measures about 4.5 million square feet (0.42 million square meters) and includes about 3.5 million square feet (0.33 million square meters) of office space. It has more than 100 elevators. The Skydeck elevator can travel to the 103rd floor in 70 seconds. The building uses about as much electric power as a town of 35,000 people.
The Willis Tower was built by Sears, Roebuck and Co. Construction on the building began in 1970 and was completed in 1974. It cost $160 million. The structure was designed by the architectural firm of Skidmore, Owings & Merrill, led by architect Bruce Graham and structural engineer Fazlur Rahman Khan. Sears, Roebuck and Co. sold the building in 1994.
See also Skyscraper.
