"The Sears Tower is the world's tallest building. The stepback geometry of the 110-story tower was developed in response to the interior space requirements of Sears, Roebuck and Company. The configuration incorporates the unusually large office floors necessary to Sears' operation along with a variety of smaller floors. The building plan consists of nine 75 x 75 foot column-free squares at the base. Floor sizes are then reduced by eliminating 75 x 75 foot increments at varying levels as the tower rises. A system of double-deck express elevators provides effective vertical transportation, carrying passengers to either of two skylobbies where transfer to single local elevators serving individual floors occurs."

—from Bruce Graham. Bruce Graham of SOM. p56.

The Creator's Words

"Tall buildings are man-made. Towers have historically been not only the pride of their temporary owners, but of their cities as well. So the Sears Tower, one more mountain, was created for this city on the plains. Sears is very direct in its structural solution, a new concept of cluster tubes, originally fifteen, reduced to nine when the hotel was eliminated from the plan. The Sears Tower itself is much like the idea behind San Gimignano, but unlike most tall buildings in New York, it is a tower of the people, not the palace of a bank."

—Bruce Graham. from Bruce Graham. Bruce Graham of SOM. p56.

Details

1450 feet tall (1468 or 1470 feet by some sources) — about 100 feet taller than the World Trade Center twin towers.
110 stories (109 stories by some sources)
4.4 million square feet — second in office space area only to the Pentagon

The plan consists of a square bundle of 9 square tubes, each 75 feet on a side. All nine tubes reach up through the 49th floor, where three terminate. Two more opposite corner tubes terminate at a slightly higher floor, two more end with the 91st floor, and two tubes extend to the full height.