The Willis Tower is a skyscraper in Chicago, Illinois. Sears, Roebuck and Company paid for the building to be built in August 1970 and it was called the Sears Tower until 2009. The building was finished in 1974. The Willis Tower is the tallest building in North America and was the tallest building in the world from 1974 to 1996. It has 108 levels, and from the ground to the roof it is 442 m (1,451 ft) tall.
Before the Willis Tower was completed, the tallest building in the world was the World Trade Center. In 1996, the Petronas Twin Towers in Kuala Lumpur, Malaysia became the world's tallest buildings. The Willis Tower is still the tallest building in the world from ground to pinnacle because it has two television antennas on top of it. From the ground to the top of the taller antenna is 527 m (1,730 ft).