The Willis Tower, formerly known as the Sears Tower, is a 108-story, skyscraper in Chicago, Illinois. The tower has 108 stories, though the building's owners count the main roof as 109 and the mechanical penthouse roof as 110. When it finished costruction in 1973, it beat the World Trade Center in New York City to become the tallest building in the world. It was the tallest building in the world for twenty-five years until the Petronas Towers were built in Malaysia. It was also the tallest building in the Western Hemisphere for 41 years, until the new One World Trade Center beat it in 2013.
Willis Tower is seen as the best work of architect Fazlur Khan. As of 2021, it is the third-tallest building in the United States and the Western hemisphere. It is also the 23rd-tallest in the world. Each year, more than one million people visit its observation deck, the highest in the United States. It is one of Chicago's most popular tourist places. The tower was renamed in 2009 after the Willis Group bought the tower.
The building's largest office partner is United Airlines, which moved its corporate headquarters from 77 West Wacker Drive in 2012. Other major company offices in the tower include Schiff Hardin and Seyfarth Shaw. Morgan Stanley moved into the tower in 2019.
It was known as the Sears Tower until 2009, as it was the headquarters of retail company Sears from its opening in 1974. Many people from Chicago still call the tower by its original name.
History
Planning and construction
In 1969, Sears, Roebuck & Co. was the largest retailer in the world, with about 350,000 employees. Sears wanted to put many of its employees into one building on the western part of Chicago's Loop. The company was given a location by West Chicago Loop not far from Grant Park. Sears eventually bought the West Chicago loop location and bought 15 old buildings from 100 owners and paid $2.7 million to the city. Sears and the city of Chicago approved the design and construction began in April 1971. Sears needed of office space for its planned tower. They hired architects Skidmore, Owings & Merrill (SOM). Sears paid for construction of the building. Architects Bruce Graham and Fazlur Khan designed the building. They designed it as a nine square "tubes". It was connected in a 3×3 metal wrap forming a square base with sides. All nine tubes would rise up to the 50th floor of the building, where the northwest and southeast tubes end. The northeast and southwest tubes reach the 66th floor with the north, east, and south tubes end at the 90th. The last west and center tubes reach 108 floors. The Sears Tower was the first building to use this design. It was both cheaper and stronger. At 1,450 feet, it had more space and was higher than the Empire State Building. It cost much less per unit area. The system became successful in skyscraper construction and has been used in most supertall buildings.
With the floors left over Sears decided to rent them to other companies for offices. Small metal floors were added to give enough space to people working in the tower. Skidmore architects proposed a tower with large, floors in the lower part of the building. They also added metal floors with many setbacks, which would give the tower its well known look.
The tower passed the height of New York's unfinished World Trade Center to become the world's tallest building. The height was limited by the Federal Aviation Administration (FAA) to protect air traffic. Two antennas were added at the top of the building for television and radio broadcasting. The building was completed in May 1973 and opened the next year. Construction cost about US$150 million.
Black bands appear on the tower around the 29th–32nd, 64th–65th, 88th–89th, and 104th–108th floors. These give the building's environmental support systems and hide its belted trusses. Even though adding a fire sprinkler system was not forced, the building was built with one from the beginning. There are around 40,000 sprinkler heads in the building. They cost $4 million.
In February 1982, two television antennas were added to the building, increasing its total height to . The western antenna was made bigger, bringing the overall height to on June 5, 2000. It was done to improve reception of local NBC station WMAQ-TV.
Legal action
As the construction of the building reached as the 50th floor in 1972, people sued Sears and wanted to stop the building from passing 67 floors. The lawsuits said that above the 67th floor would make television signals bad.