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Of the fifteen tallest buildings in the United States, five are in Chicago. Chicago has the second-tallest skyline in the United States after New York City. Chicago leads the nation in the twenty tallest women-designed towers in the world, thanks to contributions by Jeanne Gang and Natalie de Blois.
It is the third-tallest building in the Western Hemisphere, as well as the 23rd-tallest in the world. Each year, more than 1.7 million people visit the Skydeck observation deck, the highest in the United States, making it one of Chicago's most popular tourist destinations.
Willis Tower, formerly known as Sears Tower, is 110 stories high and was the tallest building in the world when it opened in 1973. Learn about its history, evolution, amenities, and broadcast facility on its official website.
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Willis Tower, skyscraper office building in Chicago, Illinois, located at 233 South Wacker Drive, that is one of the world’s tallest buildings. The Sears Tower opened to tenants in 1973, though construction was not actually completed until 1974. Built for Sears, Roebuck and Company, the structure reaches 110 floors and a height of 1,450 feet (442 m...
In 1969 Sears, Roebuck and Company was the world’s largest retailer, employing approximately 350,000 people. In order to consolidate current staff and accommodate anticipated growth, the company hired SOM to design a three-million-square-foot office tower. The location of the tower was strategically selected for its proximity to expressways and commuter rail lines to benefit Sears employees. But in the end, the tower’s location proved to be advantageous for the city as well. The inhabitants of the bustling office building generated new energy in a formerly stagnant West Loop neighbourhood.
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This history explains why many Chicagoans still nostalgically refer to the building as the Sears Tower, although it has not technically been the Sears Tower for years. In 2009 the London-based insurance broker Willis Group Holdings (later called Willis Towers Watson) leased more than 140,000 square feet of office space on three floors of the Sears Tower. The contract included naming rights for 15 years. On July 16, 2009, the name of the building was officially changed to Willis Tower.
Welded steel frames form vertical tubes that support one another to provide the rigidity needed to limit the lateral sway from wind forces. Variations in the height of each individual tube also disrupt air currents, which reduces the stress of the wind on the structure. This system minimizes the amount of structural steel required for a building of its great height. The steel was prefabricated, with nearly all welding done off the erection site and bolt connections made at the site. The innovative vertical-tube design was inspired by the uneven arrangement cigarettes make when they are pushed out of a pack. (See also building construction.)
The building is modular in plan, with nine 75-foot-square, column-free units. These nine square units compose a 225-foot-square base. At the 50th floor two diagonally opposite units stop, forming the first step back. The second step back is at the 66th floor with the other two diagonal units stopping, and the last at the 90th floor with three units stopping, leaving an upper tower of 20 stories.
The exterior is sheathed in black aluminum and bronze-tinted glass. Black bands appear around the building at the 30th–31st, 48th–49th, 64th–65th, and 106th–108th floors, at which points louvers clad the areas devoted to mechanical operations of the building. In the lobby is a major work by the American sculptor Alexander Calder, an enormous motorized mural named Universe, which he called a “wallmobile.” The tower’s observation deck, the Skydeck, is located on the 103rd floor. In the early 21st century the Skydeck underwent a major renovation that included addition of The Ledge, four glass boxes that extend 4.3 feet (1.3 metres) from the building; The Ledge opened in 2009, offering unobstructed views of Chicago and the outlying area.
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The Sears Tower was the world’s tallest building until 1996, when it was surpassed by the Petronas Twin Towers (1,483 feet [451.9 metres]) in Kuala Lumpur, Malaysia. (See Researcher’s Note: Heights of Buildings.)
The tallest building in the city is the 110-story Willis Tower, which rises 1,451 feet (442 m) in the Chicago Loop and was completed in 1974. Sears Tower was the tallest building in the world upon its completion, and remained the tallest building in the United States until May 10, 2013.
Learn about the Willis Tower, formerly the Sears Tower, the 12th tallest building in the world and the iconic landmark of Chicago's skyline. Find out its history, construction, design, features, and how to visit the observation deck on the 103rd floor.
Apr 25, 2017 · Learn about the history and features of the tallest buildings in Chicago, including the Willis Tower, the former Sears Tower and the world's tallest for 25 years. See the rankings, heights, floors and photos of the top 20 skyscrapers in the city.
