Sears Tower Tallest Building. When was the sears tower the tallest building in the world? Chicago’s tallest building the willis tower (formerly known as sears tower) is the city’s tallest building completed in 1973.

As designed by architect bruce graham and engineer fazlur khan of the chicago office of skidmore owings and merrill (som), the structure was a bundled tube system of nine squares with sides of 75 feet (for an overall 225 x 225 ft), sheathed in a. As designed by architect bruce graham and engineer fazlur khan of the chicago office of skidmore owings and merrill (som), the structure was a bundled tube system of nine squares with sides of 75 feet (for an overall 225 x 225 ft), sheathed in a. I love the sears tower and don't really give a damn if it was the 20th tallest in the world.