Sears Tower, Chicago, the world's third tallest building. Until the opening of the 1,483-ft (452-m) Petronas Towers (1997) in Kuala Lumpur, Malaysia, it was the world's tallest building. Constructed from 1970 to 1974 for Sears, Roebuck & Co., it rises 110 stories to a height of 1,450 ft (442 m); the 253 ft (77 m) television antenna topping it makes it the world's third largest freestanding structure at 1,703 ft (519 m). Designed by the firm of Skidmore, Owings and Merrill, the Sears Tower is supported structurally by square tubes of welded steel with floors suspended within the tubes, a technological innovation that was developed specifically for the mammoth skyscraper by architectural engineer Fazlur Kahn. The Sears Tower has an exterior of black aluminum and bronze-toned glass cut by black bands.

Skyscraper office building in Chicago. With 110 floors and a height of 1,450 ft (442 m), it became the world's tallest building at its completion in 1974. Its architect, Fazlur Khan (1928–1982), designed it as a bundled-tube (see skyscraper) structure to resist lateral forces. It is modular in plan, with nine 75-ft- (23-m-) square, column-free units. The exterior is sheathed in black aluminum and bronze-tinted glass. Louvers clad the four floors devoted to the building's mechanical operations. It was the world's tallest building until 1996, when it was surpassed by the Petronas Towers (1,483 ft [452 m]) in Kuala Lumpur, Malaysia.

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