Willis Tower

The Willis Tower, formerly and still commonly referred to as the Sears Tower, is a 110-story, 1,451-foot (442.3 m) skyscraper in the Loop of Chicago, Illinois, United States. Designed by architect Bruce Graham and engineer Fazlur Rahman Khan of Skidmore, Owings & Merrill (SOM), it opened in 1973 as the world's tallest building, a title that it held for nearly 25 years. It is the third-tallest building in the Western Hemisphere, as well as the 26th-tallest in the world. Each year, more than 1.7 million people visit the Skydeck, the highest observation deck in the United States, making it one of Chicago's most popular tourist destinations. Due to its height and location, the tower is visible from a great distance. The building has appeared in numerous films and television shows set in Chicago.

The building occupies a site bound by Franklin Street, Jackson Boulevard, Wacker Drive, and Adams Street. Graham and Khan designed the building as nine square "tubes", clustered in a 3×3 matrix; seven of the tubes set back at upper floors. The tower has 108 stories as counted by standard methods, though the building's owners count the main roof as 109 and the mechanical penthouse roof as 110. The facade is made of anodized aluminum and black glass. The base of the building contains a retail complex known as the Catalog. The lower half of the tower was originally occupied by retail company Sears, which had its headquarters there until 1994, while the upper stories were rented out.

The structure was known as the Sears Tower from its construction until the naming rights were included in a 2009 lease with the Willis Group. Local area residents still refer to the building by its old name.