The structure is built using a steel-framed bundled-tube construction technology. The building was finished in May 1973. Until 1998, the Willis Tower was the highest structure in the world. After 18 years, Sears Roebuck & Company sold the tower and relocated. In 2006, American Airlines bought the tower for $175 million and renamed it the American Airlines Center.
Willis Tower is currently the second tallest building in Chicago after Trump International Hotel and Tower. It has been listed as one of the "Top 10 Tallest Buildings in the World" since its completion.
Willis Tower is also known as "Cloud City" due to its appearance from certain angles. The name comes from J.W. Willis, who designed the original plan for the building site. Before deciding on a name for the building, Willis' design team went through several proposals including "Campus Martius", "Chrysler Headquarters", and "Illinois Central Plaza".
Willis Tower has 49 floors above ground and 1 floor below ground. Its total height is 468 feet (141 m). The spire, which reaches 541 feet (163 m), is the highest point in Chicago. The base of the spire is painted red, white, and blue to represent the flags of United States, Canada, and Illinois respectively.
Willis Tower is Chicago's highest structure. The structure, which was completed in 1973, held the title of "World's Tallest" for 25 years. It was the tallest skyscraper in the United States until 2013, when One World Trade Center surpassed it. The Sears Corporation sold the skyscraper in 1994 but retained name rights until 2003. It is now owned by a real estate investment trust that also owns another high-rise building in Chicago.
When measured from its foundation to its top, Willis Tower is 1,453 feet (442 m) tall. Its spire is 45 feet (13.7 m) wide at its base and rises another 108 feet (32 m) before terminating in a stainless steel ball on a gantry platform. The tower has 72 floors above its basement level; its observation deck is on floor 71.
Willis Tower was designed by the Chicago architectural firm of Graham, Anderson, Probst & White and built by the General Building Contractors Association. The tower cost $150 million to construct. At the time it was built, it was considered one of the most expensive buildings in American history. Although not a museum or an attraction itself, the 103rd floor of Willis Tower serves as a viewing platform accessible to visitors via the Skydeck Ledge. A glass elevator takes visitors up to the top in just over three minutes.
Willis Tower is used primarily for business offices, but it also contains several luxury hotel rooms and apartments.
Join Britannica's Publishing Partner Program and our professional network to earn worldwide exposure for your work! Willis Tower, previously Sears Tower (1973–2009), is a skyscraper office building situated at 233 South Wacker Drive in Chicago, Illinois, and is one of the world's highest structures. The building is named after its primary tenant, the Chicago-based insurance company J.L. Saunders Company.
Willis Tower is the second-highest building in the United States, behind the IBM Building in New York City. It is also one of the tallest buildings in the Western Hemisphere. When it was built, it was the largest structure in the world by volume of concrete used in its construction. With a height of 1,729 feet (541 m) and a width of 98 feet (30 m), the Willis Tower is also the widest building on an individual basis. The building has 47 floors above the ground floor, but only the first 42 floors are fully occupied while the other 5 are vacant.
It was designed by the Chicago architectural firm Adler and Sullivan, with structural engineering by F.J. Otto & Co. Construction began in 1973 and was completed in 1979. At the time of its opening, the Willis Tower was the world's tallest building without elevators; today it is ranked third behind the Taipei 101 and Shanghai World Financial Center.
During the 1960s and 1970s, he rose to prominence with his designs for Chicago's 100-story John Hancock Center and the 110-story Sears Tower, later renamed Willis Tower and the tallest structure in the world from 1973 until 1998. Although he died before either building was completed, his designs are important factors in their success today.
Fazlur Rahman Khan was born on April 20, 1911 in Cawnpore, India. He received his early education in India before moving with his family to America when he was 15 years old. He studied architecture at the Illinois Institute of Technology in Chicago and became one of the first Indian architects in the United States.
Khan began his professional career in 1934 with the architectural firm of Graham, Anderson, Probst and White in Chicago, where he worked until 1940. It was here that he met his future wife, Helene "Nell" Walker, who was also an architect. The two married in 1939 and had a son together named Faisal. In 1940, he moved back to India to take charge of his own office where he designed many famous buildings including the Central Bank of India in Mumbai.
In 1958, he returned to Chicago where he joined the John Hancock Center team as chief architect. The project was very large and required much expertise from an Indian architect like Fazlur Khan.