The Sears Tower is a supertall skyscraper in Chicago, Illinois, and the tallest building in Illinois as well as in the United States since 1973, surpassing the World Trade Center, which itself had surpassed the Empire State Building only a year earlier. Commissioned by Sears, Roebuck and Company, it was designed by chief architect Bruce Graham and structural engineers Srinivasa and Fazlur Khan of Skidmore, Owings and Merrill.
Construction commenced in August 1970 and the building reached its originally anticipated maximum height on May 3, 1973. When completed, the Sears Tower had overtaken the roof of the World Trade Center in New York City as the world's tallest building. The tower has 108 stories as counted by standard methods, though the building owners count the main roof as 109 and the mechanical penthouse roof as 110. The distance to the roof is 442 m (1,450 ft 7 in), measured from the east entrance.
In February 1982, two television antennas were added to the structure, increasing its total height to 520 m (1,707 ft). The western antenna was later extended to 527 m (1,729 ft) on June 5, 2000 to improve reception of local NBC station WMAQ-TV.
Black bands appear on the tower around the 29th–33rd, 64th–66th, 88th–90th, and 104th–109th floors. These are louvers which allow ventilation for service equipment and obscure the structure's belt trusses which Sears Roebuck did not want to be visible as on the John Hancock Center. The Sears Tower has the second most total floor space of any building in the United States, only behind The Pentagon.