Willis Tower (The Sears Tower)

Tower of Willis (Willis Tower or the Sears Tower was once known) is a skyscraper in Chicago, Illinois. This building is the tallest building in the United States since 1973 after defeating the height of World Trade Center. Previously, the World Trade Center is the tallest building in the U.S. for a year after surpass the Empire State Building located in the same city, New York City. Sears Tower was built retail conglomerate Sears, Roebuck and Company. Chief designer was the architect Bruce Graham and structural engineer Fazlur Khan of Skidmore, Owings and Merrill. 

Construction began in August 1970, and reached a maximum building height as planned on May 3, 1973. When finished, the height of the Sears Tower surpassed the World Trade Center in New York City, and became the tallest building in the world. This building consists of 108 floors, but the roof of the building owners count the floor as a floor 109, and the top that contains mechanical equipment as the floor 110. High building to the roof is 442 m, calculated from the entrance to the east. 

In February 1982, two television antennas mounted on top of buildings so that the height of the tower was increased to 520 m. Furthermore, on June 5, 2000, the antenna on the western side was extended to 527 m to improve reception of local television station WMAQ-TV is the NBC television network.

On August 12, 2007, the developer of Burj Dubai in Dubai, United Arab Emirates reported that the height of the tower was being erected have surpassed the Sears Tower in all categories of building height. The Burj Dubai has surpassed the Sears Tower with an antenna height (527.3 m ), and now the Burj Dubai height of at least 585.7 m, or 58.4 meters taller than the Sears Tower.

In March 2009, an insurance company based in London, Willis Group Holdings, Ltd.., Agreed to borrow three floors of the Sears Tower and has the right name for the Sears Tower as part of the agreement. On July 16, 2009, Sears Tower officially changed its name to Tower of Willis.

Location: Chicago, Illinois USA

Status: Completed construction

Built: 1970-1974

Height Antennas / top: 527 m

Height Roof: 442 m

Number of floors: 108

Architect: Skidmore, Owings and Merrill

Floor area of 418.064 m² (353.961 m² for lease) 

The number of elevator 104, with 16 two-story elevator