Chicago Architecture Info

The Willis Tower



Address 233 South Wacker Drive, Chicago, Illinois 60606
Bounding streets
  • Upper South Wacker Drive
  • Lower South Wacker Drive
  • West Jackson Boulevard
  • South Franklin Street
  • West Adams Street
Neighborhood The Loop
Formerly Sears Tower
Formerly The Sears Building
Built 1970 - 1974
Architecture firm Skidmore, Owings & Merrill
Architect Bruce Graham
Structural engineer Fazlur R. Khan
Cost $186,000,000
  • Observation deck
  • Office
  • Retail
  • Skyscraper
Floors 110
Missing floor Level 109. The building owners count the roof as 109.
Disputed floor The mechanical penthouse for the elevators. Some buildings count this as a floor, some do not. This building does.
Height to the tip of the west antenna mast 1,729 feet
Height to the tip of the east antenna mast 1,709 feet
Height to roof 1,450 feet, seven inches
Height to glass observation boxes 1,353 feet
Width 195 feet
Total floor space 4,560,000 square feet
Rentable floor space 3,800,000 square feet
Weight 445,000,000 pounds
Caissons 114
Elevators 104 total. 14 are double-decker.
Observatory elevators speed 18.2 miles per hour
Windows More than 16,100
Property size 2.96 acres
Parking spaces 160
Plumbing More than 25 miles
Electrical lines More than 1,500 miles
Elevator cables More than 80 miles


  • West Quincy Street was removed to make way for this tower. The developers purchased it from the City of Chicago for $2,767,500.
  • The original plan for this building was just 70-stories tall.
  • Before construction, models of the this tower with the rest of the city were built and tested in a wind tunnel at the University of Western Ontario.
  • The last steel beam put into place in the construction of this building on the 110th floor was signed by over 12,000 Chicagoans.
  • The building, itself, does not have a tuned mass dampener, which is common on large skyscrapers. But both of the two large antenna masts has one of its own near the top.
  • The building's exterior is black anodized aluminum. The windows are tinted bronze.
  • According to the Chicago Sun-Times, in 2005 a deal was in the works for CDW to move to this building, which included naming rights. The deal fell apart because the building's owners didn't want the word “Discount” on the tower.
  • The building has an average sway of six inches off center.
  • Alain Robert told Vancouver 24 Hrs that this building was his favorite illegal climb.


April 6, 1973 Two women were hit by pieces of falling wood that broke loose from construction work on the 108th floor.
May 3, 1973 This building was topped off, and became the tallest building in the world. A title it would hold for 25 years.
May 1973 This building opened to the public.
1974 The observation deck opened.
1981 Dan Goodwin climbed the outside of this building.
1989 This building was sold to AEW for $800,000,000.
1992 Sears moved out of this building to the suburbs.
1997 This building was sold for $804,000,000 to TrizecHahn.
1998 This building illuminated its antenna masts in Christmas colors for the first time.
1999 Alain Robert climbed the exterior of this building.
September 11, 2001 This building's observation deck was closed after the terrorist attacks the World Trade Center and the Pentagon.
October 29, 2001 The observation deck reopened.
2003 Sears' naming rights to this building expired. There was no company willing to buy the rights immediately, so the name remained Sears Tower.
August 2003 Trizec Properties surrendered the building to MetLife.
January 15, 2004 The Chicago Tribune reported that the Sears Tower would be equipped with cellular repeaters. This was to help cell phone users who have a hard time making and receiving calls in the tower because of its structure, and the fact that cell phone users inside the building can be a thousand feet higher than the nearest cell phone tower.
March 11, 2004 This building was sold to Jeffrey Feil and Joseph Chetrit by MetLife for $835,000,000.
September 25, 2005 An investigation by Emporis determined the actual correct height to the main roof of this building is 1,450 feet, seven inches.
May 23, 2006 Seven people were arrested in Miami for allegedly plotting to launch a terrorist attack on this building.
January 19, 2007 This building was sold for $385,000,000.
February 1, 2008 Several women walking by this building were shocked by electrical currents from the sidewalk. The stray voltage leaked from the system which automatically de-ices the sidewalk when it snows (a common device for large buildings in cold climates). The system was turned off until it could be fixed.
March 11, 2009 The Wall Street Journal reported insurance giant The Willis Group was considering consolidating its offices in this building, and if that happened it would be renamed The Willis Tower.
March 12, 2009 The Willis Group announced it would move nearly 500 employees to this building in a deal that included renaming the building The Willis Tower. It did not pay extra for the naming rights.
April 21, 2009 The Sears Tower signs on this building were temporarily covered by by Willis Tower banners as decisions were made about out how many Willis signs to hang, and where.
May 1, 2009 A plan was announced to add a glass-floored outdoor viewing gallery to the observation level.
June 24, 2009 A plan was announced to give this building a $350,000,000 environmental facelift. The plan included the possibility wind turbines and greenery on the roofs, replacing all of the building's windows, and changes to the building's mechanical systems to make them more energy efficient. The goal was to reduce the building's energy use by 80%. However, earlier thoughts about painting the building silver were thrown out.
July 1, 2009 New Willis Tower signs went up. The Sears Skydeck was renamed Skydeck Chicago.
July 2, 2009 The 103rd-floor outboard glass viewing platforms known as “The Ledge” opened to the public.
July 16, 2009 In a ceremony, the building name officially changed from Sears Tower to Willis Tower.
September 2010 This building was ranked #10 on Chicago Magazine's list of the Top 40 Buildings in Chicago.