The Sears Tower, recently renamed as the "Willis Tower," is a privately built spectacular skyscraper in Chicago which stands at 108 stories. It was completed in 1973 and eclipsed the World Trade Center in New York as the tallest building in the United States, a title it holds to this day.
It is a marvel of engineering, sustaining the high winds in Chicago so well that the maximum wind draft at the top of the building is merely one foot. Its successful design consists of:
- revolutionary bundled-tube structural design. ... The Sears Tower is actually a bundle of nine tubes, and is considered one of the most efficient structures designed to withstand wind. This is a great design for a skyscraper in Chicago, the "Windy City," where the average wind speed is 16 miles per hour. As the building climbs upward, the tubes begin to drop off, reducing the wind forces on the building. The Tower's heavy weight -- more than 440 million pounds -- is also supported by 114 piles sunk deep into the earth so that they stand firmly on hard, solid bedrock.
From the Visitor Skydeck at the top, one can see four states on a clear day: Illinois, Indiana, Michigan and Wisconsin.