Seen in 1998 (as Sears Tower)
|Former names||Sears Tower (1973–2009)|
|Tallest in the world from 1973 to 1998[I]|
|Preceded by||World Trade Center (1970)|
|Surpassed by||Petronas Twin Towers|
|Type||Office, observation, communication|
|Location||233 S. Wacker Drive|
Chicago, Illinois 60606
|Current tenants||United Airlines|
|Named for||Willis Group Sears (1973–2009)|
|Architectural||442.1 m (1,450 ft)|
|Tip||527 m (1,729 ft)|
|Top floor||412.7 m (1,354 ft)|
|Floor count||108 (+3 basement floors), 110 floors including mechanical.|
|Floor area||416,000 m2 (4,477,800 sq ft)|
|Lifts/elevators||104, with 16 double-decker elevators, made by Westinghouse, modernized by Schindler Group|
|Design and construction|
|Architect||Skidmore, Owings and Merrill |
Fazlur Rahman Khan
|Main contractor||Morse Diesel International|
|I. ^ Willis Tower at Emporis|
The Willis Tower, built as and still commonly referred to as the Sears Tower, is a 110-story, 1,450-foot (442.1 m) skyscraper in Chicago, Illinois. At completion in 1973, it surpassed the World Trade Center towers in New York to become the tallest building in the world, a title it held for nearly 25 years; it remained the tallest building in the Western Hemisphere until the completion of a new building at the rebuilt World Trade Center site in 2014. The building is considered a seminal achievement for its designer Fazlur Rahman Khan. The Willis Tower is the second-tallest building in the United States and the Western hemisphere – and the 16th-tallest in the world. More than one million people visit its observation deck each year, making it one of Chicago's most-popular tourist destinations. The structure was renamed in 2009 by the Willis Group as part of its lease on a portion of the tower's space.
As of April 2018[update], the building's largest tenant is United Airlines, which moved its corporate headquarters from the United Building at 77 West Wacker Drive in 2012 and today occupies around 20 floors with its headquarters and operations center. Other major tenants include the building's namesake Willis Group and the law firms of Schiff Hardin and Seyfarth Shaw. Morgan Stanley plans to move to the building in 2019, and to become the building's fourth-largest tenant by 2020.
- 1 History
- 2 Skydeck
- 3 Height
- 4 Naming rights
- 5 Figures and statistics
- 6 Broadcasting
- 7 Cultural depictions
- 8 Image gallery
- 9 See also
- 10 References
- 11 External links
Planning and construction
In 1969, Sears, Roebuck & Co. was the largest retailer in the world, with about 350,000 employees. Sears executives decided to consolidate the thousands of employees in offices distributed throughout the Chicago area into one building on the western edge of Chicago's Loop. Sears asked its outside counsel, Arnstein, Gluck, Weitzenfeld & Minow (now known as Arnstein & Lehr, LLP) to suggest a location. The firm consulted with local and federal authorities and the applicable law, then offered Sears two options: the Goose Island area northwest of downtown, and a two-block area bounded by Franklin Street on the east, Jackson Boulevard on the south, Wacker Drive on the west and Adams Street on the north, with Quincy Street running through the middle from east to west.
This latter site was decided upon, and preliminary inquiries determined that the necessary permits could be obtained and Quincy Street vacated. The next step was to acquire the property; a team of attorneys from the Arnstein law firm, headed by Andrew Adsit, began buying the property parcel by parcel. Sears purchased 15 old buildings from 100 owners and paid $2.7 million to the City of Chicago for the portion of Quincy Street that divided the property.
Sears, which needed 3,000,000 square feet (280,000 m2) of office space for its planned consolidation and predicted that growth would require yet more, commissioned architects Skidmore, Owings & Merrill (SOM) to produce a structure to be one of the largest office buildings in the world. Their team of architect Bruce Graham and structural engineer Fazlur Rahman Khan designed the building as nine square "tubes" (each essentially a separate building), clustered in a 3×3 matrix forming a square base with 225-foot (69 m) sides. All nine tubes would rise up to the 50th floor of the building. At the 50th floor, the northwest and southeast tubes end, and the remaining seven continue up. At the 66th floor, the northeast and the southwest tubes end. At the 90th floor, the north, east, and south tubes end. The remaining west and center tubes continue up to the 108th floor.
The Sears Tower was the first building to use Khan's bundled tube structure. This innovative design was structurally efficient and economic: at 1,450 feet, it provided more space and rose higher than the Empire State Building, yet cost much less per unit area. This structural system would prove highly influential in skyscraper construction. It has been used in most supertall buildings since then, including the world's tallest building, the Burj Khalifa. To honor Khan's contributions, the Structural Engineers Association of Illinois commissioned a sculpture of him for the lobby of the Willis Tower.
Sears executives decided that the space they would immediately occupy should be efficiently designed to house their Merchandise Group, and that floor space for future growth would be rented out to smaller firms and businesses until Sears could retake it. The latter floor areas had to be designed to a smaller plate, with a high window-space to floor-space ratio, to be attractive and marketable to prospective lessees. Smaller floorplates required a taller structure to yield sufficient square footage. Skidmore architects proposed a tower with large 55,000-square-foot (5,100 m2) floors in the lower part of the building, and gradually tapered areas of floorplates in a series of setbacks, which would give the Sears Tower its distinctive look.
As Sears continued to offer optimistic projections for growth, the tower's proposed floor count rapidly increased into the low hundreds, surpassing the height of New York's unfinished World Trade Center to become the world's tallest building. The height was restricted by a limit imposed by the Federal Aviation Administration (FAA) to protect air traffic. The financing of the tower was provided by the Sears company. It was topped with two antennas 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 completed in May 1973. The construction cost about US$150 million at the time, equivalent to $830 million in 2018. By comparison, Taipei 101, built in 2004 in Taiwan, cost around the equivalent of US$2.21 billion in 2018 dollars.
Black bands appear on the tower around the 29th–32nd, 64th–65th, 88th–89th, and 104th–108th floors. These are louvres that allow ventilation for service equipment and obscure the structure's belt trusses. Even though regulations did not require a fire sprinkler system, the building was equipped with one from the beginning. There are around 40,000 sprinkler heads in the building, installed at a cost of $4 million.
In February 1982, two television antennas were added to the structure, increasing its total height to 1,707 feet (520.3 m). The western antenna was later extended, bringing the overall height to 1,729 feet (527 m) on June 5, 2000, to improve reception of local NBC station WMAQ-TV.
Suits filed to halt construction
As the construction of the building neared the 50th floor, lawsuits for an injunction were filed seeking to stop the building from exceeding 67 floors. The suits alleged that above that point television reception would deteriorate and cause property values to plummet. The first suit was filed by the State's Attorney in neighboring Lake County on March 17, 1972. A second suit was filed on March 28 in the Cook County Circuit Court by the Villages of Skokie, Northbrook and Deerfield, Illinois.
Sears filed motions to dismiss the Lake County and the Cook County lawsuits and on May 17, 1972, Judge LaVerne Dickson, Chief of the Lake County Circuit Court dismissed the suit, saying, "I find nothing that gives television viewers the right to reception without interference. They will have to find some other means of ensuring reception such as taller antennas." The Lake County State's Attorney filed a Notice of Appeal and the Supreme Court agreed to permit bypassing the appellate court and to hear the matter on an expedited basis. The State's Attorney then asked the Illinois Supreme Court for a temporary injunction to stop the construction and his request was denied. On June 12, Judge Charles R. Barrett granted Sears' motion to dismiss the suit filed by the three Chicago suburbs on the grounds that interference with television reception caused by construction of the Sears building did not violate constitutional rights and that the suburbs involved in the suit do not have any right to undistorted television reception. This decision was also appealed and consolidated with the Lake County appeal with the Supreme Court of Illinois.
Meanwhile, an Illinois Citizens' Committee for Broadcasting requested the Federal Communications Commission to halt construction so that the building would not interfere with area television reception. On May 26, 1972, the Commission declined to take action on the grounds that it did not have jurisdiction to do so.
On June 30, 1972, the Illinois Supreme Court affirmed the previous rulings by Lake and Cook County Circuit Courts, by a letter order with a written opinion to follow. On September 8, 1972, the United States Court of Appeals for the Seventh Circuit upheld the decision by the Federal Communications Commission to dismiss the complaint brought by the Illinois Citizens Committee for Broadcasting charging that the building would drastically affect reception in the Chicago market and requesting the FCC to halt construction. The Supreme Court of Illinois written opinion was filed on September 20, 1972. In affirming the judgments of lower courts the Court held, "Considering the foregoing, it is clear to us that absent legislation to the contrary defendant has a propriety right to construct a building to its desired height and that completion of the project would not constitute a nuisance under the circumstances of this case." 
Sears' optimistic growth projections were not met. Competition from its traditional rivals (like Montgomery Ward) continued, with new competition by retailing giants such as Kmart, Kohl's, and Walmart. The fortunes of Sears & Roebuck declined in the 1970s as the company lost market share; its management grew more cautious. Nor did the Sears Tower draw as many tenants as Sears had hoped. The tower stood half-vacant for a decade as a surplus of office space was erected in Chicago in the 1980s.
In 1990, the law firm of Keck, Mahin & Cate decided to move out of its space in the Sears Tower and into a development that would become 77 West Wacker Drive, rebuffing Sears' attempts to entice the firm to stay. Two years later, Sears began moving its own offices out of the Sears Tower.
In 1994, Sears sold the building to Boston-based AEW Capital Management, with financing from MetLife. At the time, it was one-third vacant. By 1995, Sears had completely left the building, moving to a new office campus in Hoffman Estates, Illinois.
In 1997, Toronto-based TrizecHahn Corporation (the owner of the CN Tower at the time) purchased the building for $110 million, and assumption of $4 million in liabilities, and a $734 million mortgage. In 2003, Trizec surrendered the building to lender MetLife. In 2004, MetLife sold the building to a group of investors, including New York-based Joseph Chetrit, Joseph Moinian, Lloyd Goldman, Joseph Cayre and Jeffrey Feil, and Skokie, Illinois-based American Landmark Properties. The quoted price was $840 million, with $825 million held in a mortgage.
The building lost several major tenants in the early 2000s, due in part to perceived terrorism risk following the September 11 attacks. In June 2006, seven men were arrested by the FBI and charged with plotting to destroy the tower. Deputy FBI Director John Pistole described their plot as "more aspirational than operational". The case went to court in October 2007; after three trials, five of the suspects were convicted and two were acquitted. The alleged leader of the group, Narseal Batiste, was sentenced to 13½ years in prison in November 2009. Meanwhile, the building's largest tenant at this time, Ernst & Young, decided to move to a new building on North Wacker Drive in early 2009.
In February 2009, the owners announced they were considering a plan to paint the structure silver; this plan was later dropped. The paint would have "rebranded" the building and highlighted its advances in energy efficiency. The estimated cost was $50 million.
Since 2007, the building owners considered building a hotel on the north side of Jackson, between Wacker and Franklin, at the plaza that is the entrance to the tower's observation deck. The tower's parking garage is beneath the plaza. Building owners say the second building was considered in the original design. The plan was eventually cancelled as city zoning does not permit construction of such a tall tower there.
Although Sears' naming rights expired in 2003, the building continued to be called the Sears Tower for several years. In March 2009, London-based insurance broker Willis Group Holdings agreed to lease a portion of the building, and obtained the building's naming rights. On July 16, 2009, the building was officially renamed Willis Tower. On August 13, 2012, United Airlines announced it would move its corporate headquarters from 77 West Wacker Drive to Willis Tower.
In 2015, the Blackstone Group completed purchase of the tower for a reported $1.3 billion, the highest price ever paid for a U.S. property outside New York City. In 2017, Blackstone announced a $500 million "facelift" for the property to include a six-story commercial complex in the tower's plaza area.
The Willis Tower observation deck, called the Skydeck, opened on June 22, 1974. Located on the tower's 103rd floor, it is 1,353 feet (412.4 m) high, making it the highest observation deck in the United States and one of Chicago's most famous tourist attractions. Tourists can experience how the building sways on a windy day. They also can see far over the plains of Illinois and across Lake Michigan to Indiana, Michigan, and Wisconsin on a clear day. Elevators take tourists to the top in about 60 seconds, and allow tourists to feel the pressure change as they rise up. The Skydeck competes with the John Hancock Center's observation floor a mile and a half away, which is 323 feet (98.5 m) lower. Some 1.7 million tourists visit the Skydeck annually. A second Skydeck on the 99th floor is also used if the 103rd floor is closed. The tourist entrance can be found on the south side of the building along Jackson Boulevard.
In January 2009, Willis Tower's owners began a major renovation of the Skydeck, including the installation of retractable glass balconies, which can be extended approximately 4 feet (1.2 m) from the facade of the 103rd floor, overlooking South Wacker Drive. The all-glass boxes, informally dubbed "The Ledge", allow visitors to look through the glass floor to the street 1,353 feet (412 m) below. The boxes, which can bear 5 short tons (4.5 metric tons) of weight, opened to the public on July 2, 2009. On May 29, 2014, the laminated glass covering the floor of one of the glass boxes shattered while visitors were sitting on it, but caused no injuries. The broken glass was replaced within days, and tourist operations resumed as before.
The Willis Tower remains the second tallest building in the Americas (after One World Trade Center) and the Western Hemisphere. With a pinnacle height of 1,729 feet (527 m), it is the third-tallest freestanding structure in the Americas, as it is 86 feet (26.2 m) shorter than Toronto's CN Tower. Willis Tower is the eighth-tallest freestanding structure in the world by pinnacle height.
At 1,482.6 feet (451.9 m) tall, including decorative spires, the Petronas Twin Towers in Kuala Lumpur, Malaysia, laid claim to replacing the Sears Tower as the tallest building in the world in 1998. Not everyone agreed, and in the ensuing controversy, four different categories of "tallest building" were created. Of these, Petronas was the tallest in the first category (height to top of architectural elements, meaning spires but not antennas), giving it the title of world's tallest building.
Taipei 101 in Taiwan claimed the record in three of the four categories in 2004 to become recognized as the tallest building in the world. Taipei 101 surpassed the Petronas Twin Towers in spire height and the Sears Tower in roof height and highest occupied floor. The Sears Tower retained one record: its antenna exceeded Taipei 101's spire in height. In 2008, the Shanghai World Financial Center claimed the records of tallest building by roof and highest occupied floor.
Upon completion, One World Trade Center in New York City surpassed the Willis Tower through its structural and pinnacle heights, but not by roof, observation deck elevation, or highest occupied floor.
Until 2000, the Sears Tower did not hold the record for being the tallest building by pinnacle height. From 1969 to 1978, this record was held by the John Hancock Center, whose antenna reached a height of 1,500 feet (457.2 m), or 49 feet (14.9 m) taller than the Sears Tower's original height of 1,450 feet (442.1 m). In 1978, One World Trade Center became taller by pinnacle height due to the addition of a 359 feet (109.4 m) antenna, which brought its total height to 1,727 feet (526.4 m). In 1982, two antennas were installed on top of the Sears Tower which brought its total height to 1,707 feet (520.3 m), making it taller than the John Hancock Center but not One World Trade Center. However, the extension of the Sears Tower's western antenna in June 2000 to 1,729 feet (527 m) allowed it to just barely claim the title of tallest building by pinnacle height.
Position in Chicago's skyline
On May 25, 1981, Dan Goodwin, wearing a homemade Spider-Man suit while using suction cups, camming devices, and sky hooks, and despite several attempts by the Chicago Fire Department to stop him, made the first successful outside ascent of the Sears Tower. Goodwin was arrested at the top after the seven-hour climb, and he was later charged with trespassing. Goodwin stated that the reason he made the climb was to call attention to shortcomings in high-rise rescue and firefighting techniques. After a lengthy interrogation by Chicago's District Attorney and Fire Commissioner, Goodwin was officially released from jail.
In August 1999, French urban climber Alain "Spiderman" Robert, using only his bare hands and bare feet, scaled the building's exterior glass and steel wall all the way to the top. A thick fog settled in near the end of his climb, making the last 20 stories of the building's glass and steel exterior slippery.
Although Sears sold the Tower in 1994 and had completely vacated it by 1995, the company retained the naming rights to the building through 2003. The new owners were rebuffed in renaming deals with CDW Corp in 2005 and the U.S. Olympic Committee in 2008. London-based insurance broker Willis Group Holdings, Ltd. leased more than 140,000 square feet (13,000 m2) of space on three floors in 2009. A Willis spokesman said the naming rights were obtained as part of the negotiations at no cost to Willis, and the building was renamed Willis Tower on July 16, 2009.
The naming rights are valid for 15 years, so it is possible that the building's name could change again in 2024 or later. The Chicago Tribune joked that the building's new name reminded them of the oft-repeated "What you talkin' 'bout, Willis?" catchphrase from the 1980s American television sitcom Diff'rent Strokes and considered the name-change ill-advised in "a city with a deep appreciation of tradition and a healthy ego, where some Chicagoans still mourn the switch from Marshall Field's to Macy's". This feeling was confirmed in a July 16, 2009 CNN article in which some Chicago area residents expressed reluctance to accept the Willis Tower name, and in an article that appeared in the October 2010 issue of Chicago magazine that ranked the building among Chicago's 40 most important, the author pointedly refused to acknowledge the name change and referred to the building as the "Sears Tower". Time magazine called the name change one of the top 10 worst corporate name changes and pointed to negative press coverage by local news outlets and online petitions from angry residents. The naming rights issue continued into 2013, when Eric Zorn noted in the Chicago Tribune that "We're stubborn about such things. This month marked four years since the former Sears Tower was re-christened Willis Tower, and the new name has yet to stick."
Figures and statistics
- The top of Willis Tower is the highest point in Illinois. The tip of its highest antenna is 1,729 feet (527 m) above street level or 2,325 feet (708.7 m) above sea level, its roof is 1,450 feet 7 inches (442.14 m) above street level or 2,046 feet (623.6 m) above sea level, the 103rd floor observation deck (The Sky deck) is 1,353 feet (412 m) above street level or 1,948 feet (593.8 m) above sea level, the Franklin Street entrance is 595 feet (181.4 m) above sea level. (The highest natural point in Illinois is the Charles Mound, at 1,235 feet (376.4 m) above sea level.)
- The building leans about 4 inches (10.2 cm) towards the west due to its slightly asymmetrical design, placing unequal loads on its foundation.
- The design for Willis Tower incorporates nine steel-unit square tubes in a 3 tube by 3 tube arrangement, with each tube having the footprint of 75 ft × 75 ft (22.9 m × 22.9 m). Willis Tower was the first building for which this design was used. The design allows future growth of extra height to the tower if wanted or needed.
- The restrooms on the 103rd floor, at 1,353 feet (412.4 m) high, are the highest (relative to street level) in the Western Hemisphere.
- The design was inspired by an advertisement for a package of cigarettes.
- The Franklin Street entrance is the point from which all building heights are measured. The Wacker Drive entrance is six feet higher than the Franklin Street entrance, lower Wacker Drive/Lower Level 1 is approximately 17 feet, 6 inches lower than the Wacker Drive entrance and 11 feet, six inches lower than Franklin Street. The 103rd floor observation deck is 1,354 feet above the Franklin Street entrance. The glass ledges in the Skydeck are on a raised platform 18 inches higher than the rest of the 103rd floor or 1,349 feet, six inches above the Wacker Drive entrance, 1,355 feet, six inches above the Franklin Street entrance and 1,367 feet above lower Wacker Drive/Lower Level 1. The Skydeck elevators rise from Lower Level 2 which gives a total rise of approximately 1,382 feet to the 103rd floor.
- The building's total building area stands at 351,846 m2 (3,787,200 sq ft)
- It remains the world's tallest steel-construction building. All taller buildings use concrete or composite construction.
Many broadcast station transmitters are located at the top of Willis Tower. Each list is ranked by height from the top down. Stations at the same height on the same mast indicate the use of a diplexer into the same shared antenna. Due to its extreme height, FM stations (all class B) are very limited in power output.
Also, NOAA Weather Radio station KWO39 transmits off the top of Willis Tower, at 162.550 MHz. KWO39, programmed by the National Weather Service Weather Forecast Office in Chicago, is equipped with Specific Area Message Encoding (SAME), which sets off a siren on specially-programmed weather radios to alert of an impending hazard, such as a tornado or civil emergency.
Film and television
The building has appeared in numerous films and television shows set in Chicago such as Ferris Bueller's Day Off, where Ferris and company watch the streets of Chicago from the observation deck. The television show Late Night with Conan O'Brien introduced a character called The Sears Tower Dressed In Sears Clothing when the show visited Chicago in 2006. The building is also featured in History Channel's Life After People, in which it and other human-made landmarks suffer from neglect without humans around, and it collapses two hundred years after people are gone. In an episode of the television series Monk, Adrian Monk tries to conquer his fear of heights by imagining that he is on top of the Sears Tower. Also, in an episode of Kenan and Kel, Kenan Rockmore and Kel Kimble decide to climb to the top of the Sears Tower, so that Kenan can declare his love for a girl.
The Chicago Franchise frequently features locations where the Tower is visible in the distance.
In the movie Category 6: Day of Destruction, the tower is damaged by a tornado.
In "1969", a Season 2 episode of the science-fiction series Stargate SG-1, the SG-1 team accidentally travels back in time to the titular year. At one point, the team travels though Chicago and the Sears Tower is shown (erroneously, since construction did not begin on the tower until two years later in 1971).
In the 2004 film I, Robot, the tower is shown updated in the year 2035 with new triangular antennas. The tower is shown surpassed in height by the USR (United States Robotics) Building.
In the 2011 film Transformers: Dark of the Moon, the tower is featured in a number of scenes. The most notable one is when the N.E.S.T team tries to enter the city using V-22 Osprey helicopters. They use Willis Tower for cover before using wing suits to descend into the city streets. In the movie, the tower is shown to be severely damaged by the Decepticon invasion of the city.
In the 2014 film Divergent, the tower is shown abandoned and decayed in a future Chicago.
In the 2015 film Jupiter Ascending, the tower is featured prominently as the place where Caine and Jupiter await a spaceship to lift them off the planet.
In the 2018 film Rampage, the Energyne corporation is headquartered in the building, and uses tower's antenna to broadcast an echolocation signal that would bring three mutated monsters to town. After the antenna is destroyed by the beasts, the entire building topples to the ground.
Willis Tower as seen from John Hancock Center observation deck
View down to South Wacker Drive from the Skydeck
A view of Willis Tower at dusk
View of Willis Tower from John Hancock Center
- Architecture of Chicago
- List of buildings with 100 floors or more
- List of tallest buildings and structures in the world
- List of tallest buildings by U.S. state
- List of tallest buildings in Chicago
- List of tallest buildings in the United States
- List of tallest freestanding structures in the world
- List of tallest towers in the world
- Sears, Roebuck and Company Complex
- de la Merced, Michael J. (March 16, 2014). "Blackstone Group Purchases Landmark Willis Tower in Chicago". The New York Times. Retrieved August 11, 2015.
- "Willis Tower – The Skyscraper Center". Council on Tall Buildings and Urban Habitat. June 13, 2015. Retrieved June 13, 2015.
- The tower has 108 stories as counted by standard methods, though the building's owners count the main roof as 109 and the mechanical penthouse roof as 110. Emporis.com Retrieved on June 7, 2008
- "History and Facts - Willis Tower". willistower.com.
- "Five things you need to know about pioneering architect Fazlur Rahman Khan". The Independent. London. April 3, 2017.
-  Archived August 15, 2012, at the Wayback Machine.
- Snyder, Brett (December 16, 2013). "A Day with United Management: Elite Status, Mileage Devaluation, and Increasing Change Fees". The Cranky Flier. Retrieved December 18, 2013.
- Ecker, Danny (2018-04-16). "Morgan Stanley moving second office to Willis Tower". Crain's Chicago Business. Retrieved 2018-10-03.
- Kerch, Steve (October 20, 1991). "This job is a tall order: Sears Tower project is the height of redevelopment." Chicago Tribune.
- Arnstein & Lehr, The First 120 Years
- Chicago Tribune, December 28, 2003.
- Chicago Tribune, January 4, 1971.
- "The Tallest Skyscraper", Time, June 11, 1973
- Richard G. Weingardt (2005). Engineering Legends: Great American Civil Engineers. American Society of Civil Engineers. p. 75. ISBN 978-0-7844-7121-0.
- National Academy of Engineering (1979). Memorial Tributes. National Academies. NAP:14723.
- "Burj Dubai: The new pinnacle of vanity". Telegraph. Retrieved February 25, 2014.
- "Top 10 world's tallest steel buildings". Constructionweekonline.com. Retrieved February 25, 2014.
- "Fazlur Khan Sculpture". SEAOI. Retrieved February 25, 2014.
- "Databank: Sears Tower", Wonders of the World, PBS Databank. Retrieved November 19, 2007.
- Federal Reserve Bank of Minneapolis Community Development Project. "Consumer Price Index (estimate) 1800–". Federal Reserve Bank of Minneapolis. Retrieved January 2, 2018.
- "Inflation Calculator – Find US Dollar's Value from 1913–2015". US Inflation Calculator.
- The Times-News, February 15, 1975
- Chicago Tribune, April 9, 1972 and Chicago Tribune, May 7, 1972.
- Chicago Tribune, May 18, 1972.
- Chicago Tribune, June 10, 1972.
- Chicago Tribune, June 13, 1972.
- Chicago Tribune, July 1, 1972.
- Chicago Tribune, September 12, 1972; Illinois Citizens Committee for Broadcasting v. Federal Communications Commission, 467 F. 2d 1397 (7th Cir. 1972).
- Peo. Ex Rel. Hoogasiam v. Sears Robebuck, Ill. 52 L. 2d 301 (1972).
- For information on this transformation, see Donald R. Katz The Big Store: Inside the Crisis and Revolution at Sears, New York (Viking), 1987.
- "77 W. Wacker ready to go." Chicago Sun-Times. March 12, 1990. Retrieved on November 12, 2009.
- "Sears Picks Hoffman Estates". tribunedigital-chicagotribune. Retrieved 2018-02-09.
- Cliff Edwards, Associated Press. "TrizecHahn buys control of Chicago's Sears Tower World's 2d-tallest building sold for $110m", The Boston Globe, December 4, 1997. Retrieved February 25, 2009 from HighBeam Research
- "Sears Tower may be for sale", Crains Chicago Business, October 31, 1997
- "Trizec to sell its last local asset", Crain's Chicago Business, September 27, 2006
- "BIZ BRIEFS", Chicago Sun-Times, May 1, 2004. Retrieved February 25, 2009 from HighBeam Research
- "MetLife to Complete Sale of Chicago's Sears Tower", Chicago Tribune (Chicago, IL), April 30, 2004. Retrieved February 25, 2009 from HighBeam Research
- "Sears Tower Gets a Much-Needed New Tenant". NPR.org. Retrieved 2018-10-03.
- "FBI Killed Plot in Talking Stage". New York Times, June 24, 2006.
- "Seven charged over 'Chicago plot'". BBC News, June 23, 2006.
- "Sears Tower 'plot trial' begins", BBC News, October 3, 2007.
- "Five guilty in Chicago bomb plot", BBC News, May 12, 2009.
- "Sears Tower bomb plot leader Narseal Batiste jailed", BBC News, November 20, 2009.
- "Sears Tower to Lose Largest Tenant - The Chicago 77". www.thechicago77.com. Retrieved 2018-10-03.
- "Sears Tower in silver?", Chicago Sun-Times, February 25, 2009 Archived February 17, 2010, at the Wayback Machine.
- David Roeder. "Tall order for Tower?; Sears Tower owners to press city for zoning change, subsidy to add 2nd building as part of mega-million-dollar project next to landmark", Chicago Sun-Times, October 12, 2007. Retrieved February 25, 2009 from HighBeam Research
- "Sears Tower Being Renamed". Chicago Breaking News. March 12, 2009
- "Tallest Building in Western Hemisphere is Renamed Willis Tower" (Press release). Willis Group. July 16, 2009. Retrieved June 13, 2015.
- "Subscription Center".
- "Willis Tower in line for a $500 million facelift". Chicago Sun-Times. Retrieved 2018-10-03.
- "Sears Tower unveils 103rd floor glass balconies", USA Today, July 1, 2009
- "The Ledge at Skydeck Chicago". Archived from the original on June 8, 2011. Retrieved May 15, 2011. SOM.com Project Page
- BJ Lutz (May 30, 2014). "Coating on Willis Tower Skydeck's Ledge Cracks Under Tourists". Nbcchicago.com. Retrieved August 26, 2014.
- "Height: The History of Measuring Tall Buildings". Council on Tall Buildings and Urban Habitat. Retrieved May 1, 2012.
- "Burj Khalifa surpasses the height of Sears Tower in Chicago". Visitdubai.info. December 9, 2007. Retrieved October 31, 2011.
- "Freedom Tower ("World Trade Center 1")". NYC Tower. Archived from the original on December 21, 2008. Retrieved November 30, 2008.
- "Chicago Cubs History and News – Welcome to Just One Bad Century". Justonebadcentury.com. Archived from the original on March 20, 2012. Retrieved October 31, 2011.
- "Sears Tower in Chicago Is Scaled by Stunt Man". Chicago (Ill): New York Times. May 26, 1981. Retrieved October 31, 2011.
- "Spiderman scales Sears Tower w/Stan Lee interview". YouTube. Retrieved January 13, 2009.
- "'Spiderman' scales Sears Tower in Chicago – August 20, 1999". CNN. Retrieved September 14, 2009.
- "Sears Tower name to change to Willis Tower". Chicago Tribune. March 12, 2009. Archived from the original on April 19, 2009. Retrieved May 1, 2009.
- "Sears Tower Now Willis". Chicago Tribune. July 16, 2009. Retrieved July 16, 2009.
- Corfman, Thomas A. (March 11, 2009). "Willis could get Sears Tower naming rights". Chicago Real Estate Daily. Retrieved October 31, 2011.
- Podmolik, Mary Ellen (July 16, 2009). "Sears Tower name change: Building today officially becomes Willis Tower". Chicago Tribune. Retrieved July 16, 2009.
- Burns, Greg (July 16, 2009). "Burns on Business, Willis Wants to be Part of Chicago by Way of Jersey". Chicago Tribune. Retrieved July 16, 2009.
- Podmolik, Mary Ellen (2009). "Sears Tower name change has few Chicago fans – Willis Tower may have trouble winning over public". Chicago Tribune. The Tribune Company (March 13, 2009).
- "Sears Tower Now Named Willis Tower". CNN. July 16, 2009. Retrieved July 17, 2009.
- Johnson, Geoffrey (2010). "Top 40 Buildings in Chicago". Chicago. The Tribune Company (October 2010).
- Suddath, Claire (February 8, 2010). "Top 10 Worst Corporate Name Changes: It's the Sears Tower". TIME. Retrieved February 8, 2010.
- Zorn, Eric (2013). "Change of Subject – 'Thillens Stadium' is no more". Chicago Tribune. The Tribune Company (June 24, 2013).
- "Sears Tower". Tallest Building in the World. September 2, 2007. Retrieved September 14, 2009.
- "Why Was the Sears Tower Built?". Whyguides.com. June 5, 2000. Retrieved October 31, 2011.
- The History Channel; Modern Marvels (series); episode: The Sears Tower
- "CrediFi". Sears Tower. Retrieved September 19, 2016.
- "100 Tallest Completed Buildings in the World". Council on Tall Buildings & Urban Habitat. Retrieved 4 October 2017.
- "FM Query Results – Audio Division (FCC) USA". Fcc.gov. Retrieved September 7, 2016.
- "FM Query Results – Audio Division (FCC) USA". Fcc.gov. Retrieved September 7, 2016.
- "TV Query Results – Video Division (FCC) USA". Fcc.gov. Retrieved September 7, 2016.
- "TV Query Results – Video Division (FCC) USA". Fcc.gov. Retrieved September 7, 2016.
- "Filming Locations for Ferris Bueller's Day Off". Movie-locations.com. Retrieved September 14, 2009.
- "The Sears Tower Dressed In Sears Clothing". Nbc5.com. Archived from the original on March 2, 2008. Retrieved October 31, 2011.
- Keith Darcé (January 31, 2007). "Madison Avenue turns to Main Street | The San Diego Union-Tribune". Signonsandiego.com. Retrieved September 14, 2009.
- Merrion, Paul (September 7, 2011). "Willis Tower, CBOT Building star in Superman filming". ChicagoBusiness. Retrieved July 26, 2013.
|Wikimedia Commons has media related to Willis Tower.|
- Official website Willis Tower office-space leasing website
- Willis Tower Skydeck website
- Willis Tower on CTBUH Skyscraper Center
- Willis Tower at Emporis
- Willis Tower at Structurae
One World Trade Center (1970)
| Tallest building in the world
| World's tallest building architectural element|
| Building with the most floors
| World's tallest building rooftop
| Tallest building in the United States
One World Trade Center (2006)
| Tallest building in Chicago