The Willis Tower (aka Sears Tower) in Chicago, Illinois. Commissioned by Sears, Roebuck and Company, it was designed by chief architect Bruce Graham and structural Engineer Fazlur Khan of Skidmore, Owings, & Merrill.
The designs for the then called Sears Tower is of nine steel unit tubes. The Sears Tower project was the first building for which this design was used.
Construction commenced in August 1970, and reached its maximum height on May 3, 1973. When completed, the Sears Tower had overtaken the twin towers of the World Trade Center in New York City as the world's tallest building.
It was originally said to have 110 stories but this included the elevator penthouse and its roof; by normal counting methods it has 108. The height of the roof is 1,450 feet and 7 inches (442 m) measured from the east entrance.
The total height of the structure including the two television antennas on top added in February 1982 was 1,707 feet (520 m), the western antenna was later extended to 1,729 feet (527 m) on June 5, 2000 to improve reception of local CBS station WBBM-TV. In the process it outstripped the height of the antenna on 1 World Trade Center.
The Sears Tower also has the most total floor space of any building in the U.S. next to The Pentagon in Arlington County, Virginia. One-story black bands appear around 30th-32nd, 64th-65th, 88th-89th, and 106th-107th floors. These allow ventilation for the service equipment on those floors and obscure diagonal "X" bracing which Sears Roebuck did not want to be visible.
Who were Sears and Roebuck & Co?
Back in 1969, Sears, Roebuck & Co. were by far, the largest retailer in the world, with about 350,000 employees. Sears executives decided to consolidate the thousands of employees scattered throughout office buildings in the Chicagoland area into one building on the western edge of Chicago's Loop. With immediate space demands of 3 million square feet (300,000 mē), and with predictions and plans for future growth necessitating even more space than that, architects for Skidmore knew that the building would be one of the tallest in the city and certainly one of the largest office buildings in the world.
Sears executives decided early on that the space they would immediately occupy should be as efficiently designed to house the small army that was their Merchandise Group. However, floor space for future growth would be rented out to smaller firms and businesses until Sears could retake it. Therefore, the floor sizes would need to be smaller, with a higher window-space-to-floor-space ratio, to be more attractive and marketable to these prospective lessees. Smaller floor sizes necessitated a taller structure. Skidmore architects proposed a tower which would have large, 55,000 square foot (5,000 mē) floors in the lower part of the building, and would gradually taper the area of the floors down in a series of setbacks, which would give the Sears Tower its distinctive, husky shouldered look.
As Sears continued to offer optimistic projections for future growth, the tower's proposed height soared into the low hundreds of floors and surpassed the height of New York's unfinished World Trade Center to become the world's tallest building. Restricted in height not by physical limitation or imagination but by an artificial ceiling imposed by the Federal Aviation Administration to protect air traffic, the Sears Tower would be financed completely out of Sears' deep pockets, and topped with two antennae to permit local television and radio broadcasts. Sears and the City of Chicago approved the design, and the first steel was put in place in April 1971. The structure was complete in May of 1973. Construction costs totalled approximately $175 million USD at the time, which would be equivalent to roughly US$950 million in 2005. For comparison, Toronto's CN Tower, built in 1976, cost around the equivalent of US$260 million in 2005 dollars.
However, Sears' optimistic growth projections never came to pass. Competition from its traditional rivals (like Montgomery Ward) continued, only to be surpassed in strength by other retailing giants, like Kmart, Kohl's and Wal-Mart. Sears, Roebuck deteriorated as market share slipped away and management grew paranoid and introverted through the 1970s. The Sears Tower was not the draw Sears hoped it would be to potential lessees, and stood half vacant for a decade as more office space was built in the 1980s. Finally, Sears was forced to take out a mortgage on their headquarters building. Sears began moving its offices out of the Sears Tower in 1993 and had completely moved out by 1995, moving to a new office campus in Hoffman Estates, Illinois.
There have been several owners of the Sears Tower since then. The owners who purchased the tower in March 2004 were rumored to have plans to rename the building.
Considered one of the finest locations for business in Chicago, the Sears Tower is now a multi-tenant office building with more than 100 different companies doing business there, including major law firms, insurance companies and financial services firms.
Why the name change from Sears Tower?
The naming rights expired in 2003 and the building was still called Sears for serveral years after. In March 2009 Willis Group Holdings a broker company from London agreed to lease part of the building and also paid for the naming rights. The tower was officially renamed the Willis Tower on 16th July 2009.