Willis Tower

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Willis Tower
Sears Tower ss.jpg
Former names Sears Tower (1973–2009)
Record height
Tallest in the world from 1973 to 1998[I]
Preceded by World Trade Center (1970)
Surpassed by Petronas Twin Towers
General information
Type Office, observation, communication
Architectural style International
Location 233 S. Wacker Drive
Chicago, Illinois 60606
United States
Coordinates 41°52′44″N 87°38′09″W / 41.8789°N 87.6358°W / 41.8789; -87.6358Coordinates: 41°52′44″N 87°38′09″W / 41.8789°N 87.6358°W / 41.8789; -87.6358
Construction started 1970
Completed 1973
Height
Architectural 442.1 m (1,450 ft)[1]
Tip 527 m (1,729 ft)[1]
Top floor 412.7 m (1,354 ft)[1]
Technical details
Floor count 108[2] (+3 basement floors)
Floor area 416,000 m2 (4,477,800 sq ft)[1]
Lifts/elevators 104,[1] with 16 double-decker elevators, made by Westinghouse, modernized by Schindler Group
Design and construction
Architect Skidmore, Owings and Merrill[1] (Fazlur Khan & Bruce Graham)
References
[1]

Willis Tower (formerly named and still commonly referred to as Sears Tower) is a 108-story, 1,451-foot (442 m) skyscraper in Chicago, Illinois, United States.[2] At the time of its completion in 1973, it was the tallest building in the world, surpassing the World Trade Center towers in New York, and it held this rank for nearly 25 years. Willis Tower is the second-tallest building in the United States and the eighth-tallest freestanding structure in the world. The skyscraper is one of the most popular tourist destinations in Chicago, and over one million people visit its observation deck each year. Named the Sears Tower since its opening, the structure was renamed in 2009 by the Willis Group, as part of their lease on a portion of its space.

United Airlines moved its corporate headquarters to Willis Tower from the United Building at 77 West Wacker Drive in August 2012.[3] As of December 2013, United is the Willis Tower's largest tenant, with its headquarters and operations center occupying around 20 floors of the tower.[4]

History

Planning and construction

Breakdown of the bundled tube structure of Willis Tower with simplified floor plans

In 1969, Sears, Roebuck & Co. was the largest retailer in the world, with approximately 350,000 employees.[5] 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. After the firm consulted with local and federal authorities and the applicable law, Sears was advised that the proposed structure could be built in an area known as Goose Island, or in 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.[6] The next step was to acquire the property and a team of attorneys from the Arnstein law firm headed by Andrew Adsit began buying the property parcel by parcel.[7] Sears purchased fifteen old buildings from one hundred owners and paid $2.7 million to the City of Chicago for the portion of Quincy Street which divided the property.[8]

With immediate space demands of 3,000,000 square feet (280,000 m2), and predictions for future growth necessitating more space, Sears 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.[9] 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 Willis Tower was the first building to utilize Khan's bundled tube structure.[10] 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.[11] 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.[12][13] To honor Khan's contributions, the Structural Engineers Association of Illinois commissioned a sculpture of him[14] 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. Construction costs totaled approximately US$150 million at the time,[15] equivalent to $800 million in 2014.[16] By comparison, Taipei 101, built in 2004 in Taiwan, cost around the equivalent of US$1.76 billion in 2005 dollars.

Black bands appear on the tower around the 29th–32nd, 64th–65th, 88th–89th, and 104th–108th floors. These are louvres which 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.[17]

In February 1982, two television antennas were added to the structure, increasing its total height to 1,707 feet (520 m). The western antenna was later extended, bringing the overall height to 1,730 feet (527 m)[18] 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 Stokie, Northbrook and Deerfield, Illinois.[19]

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 stating “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.”[20] 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.[21] On June 12, Judge Charles R. Barrett granted Sears’ motion to dismiss the suit filed by three Chicago suburbs on the ground 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, too, also was appealed and consolidated with the Lake County appeal with the Supreme Court of Illinois.[22]

Meanwhile, an Illinois Citizens Committee for Broadcasting requested the Federal Communications Commission to halt construction on the grounds so that it would not interfere with area television reception. On May 26, 1972, the Commission declined to take action on the ground 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.[23] 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 Chicago land and requesting the FCC to halt construction.[24] 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.” [25]

Post-opening

Willis Tower at dusk, seen from the Loop
Willis Tower from across the Chicago River

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.[26] The Sears Tower was not the draw Sears had hoped it would be. The tower stood half-vacant for a decade as a surplus of office space was erected in Chicago in the 1980s.

By 1990, Keck, Mahin & Cate, a law firm, considered moving out of its space in the Sears Tower and moving into a potential new development, which would become 77 West Wacker Drive. Brokers who were familiar with the lease negotiations stated that Sears was trying to keep Keck, Mahin & Cate in the building. Keck, Mahin & Cate decided to move into 77 West Wacker, and the Prime Group, developer of 77 West Wacker, finalized the development of the facility. During the time that Keck, Mahin & Cate was scheduled to move out of the Sears Tower, Sears planned to move its offices to its merchandise group facilities in Hoffman Estates, Illinois.[27] Sears began moving its offices out of the Sears Tower in 1992.[citation needed]

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 vacated the building, moving to a new office campus in Hoffman Estates.[citation needed]

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.[28][29] In 2003, Trizec surrendered the building to lender MetLife.[30]

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.[31] The quoted price was $840 million, with $825 million held in a mortgage.[32]

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".[33][34] The case went to court in October 2007;[35] after three trials, five of the suspects were convicted and two were acquitted.[36] The alleged leader of the group, Narseal Batiste, was sentenced to 13½ years in prison in November 2009.[37]

Plans

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.[38]

Since 2007, the building owners have been considering 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.[39]

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.[40] On July 16, 2009, the building was officially renamed Willis Tower. On August 13, 2012, United Airlines announced it will be moving its corporate headquarters from 77 West Wacker Drive to Willis Tower.[3]

Skydeck

Three glass bottom skyboxes (top right) on the west façade of Willis Tower at the 103rd floor
View looking down from glass balcony
Glass balcony at the skydeck

The Sears Tower observation deck, called the Skydeck, opened on June 22, 1974. Located on the 103rd floor of the tower, it is 1,353 feet (412 m) high and is one of the most famous tourist attractions in Chicago. Tourists can experience how the building sways on a windy day. They 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 m) lower. Some 1.3 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.[41][42] However 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.[43]

Panorama of Chicago skyline as seen from Willis Tower Skydeck

Climbing

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 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 released.[44][45][46]

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.[47]

Address

The building's official address is 233 South Wacker Drive, Chicago, Illinois 60606.

Height

Burj Khalifa, Dubai
CN Tower, Toronto
• Willis Tower, Chicago

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 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.[48] 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 the 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.

On August 12, 2007, the Burj Khalifa in Dubai, United Arab Emirates was reported by its developers to have surpassed the Sears Tower in all height categories.[49]

Upon completion, One World Trade Center in New York City surpassed Willis Tower through its structural and pinnacle heights, but not by roof, observation deck elevation or highest occupied floor.[50]

Until 2000, the Sears Tower did not hold the record for 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 1,451 feet (442 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 1,730 feet (530 m) allowed it to just barely claim the title of tallest building by pinnacle height.

Naming rights

West facade and entrance

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,[51][52][53] and the building was renamed Willis Tower on July 16, 2009.[54]

The naming rights are valid for 15 years, so it is possible that the building’s name could change again in 2024 or later.[55] 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[54] 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".[56] 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,[57] 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".[58] 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.[59] 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."[60]

Cultural depictions

Willis Tower as viewed from Chicago's Chinatown

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.[61] 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.[62] 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.[63] 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.

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 2013 film, Man of Steel, the tower's interior and parts of its exterior portrayed the offices of the Daily Planet.[64]

In the film Divergent, the tower is shown abandoned and decayed in a future Chicago.

Other

Older versions of Microsoft Flight Simulator would begin with the player on the runway of Meigs Field, facing a virtual version of the tower.

In Sufjan Stevens' 2005 album Illinois, the tower is referenced in the track "Seer's Tower", whose title is a play on the tower's now-former name, Sears Tower.

Position in Chicago's skyline

311 South Wacker Willis Tower Chicago Board of Trade Building 111 South Wacker AT&T Corporate Center Kluczynski Federal Building CNA Center Chase Tower Three First National Plaza Mid-Continental Plaza Richard J. Daley Center Chicago Title and Trust Center 77 West Wacker Pittsfield Building Leo Burnett Building The Heritage at Millennium Park Crain Communications Building IBM Plaza One Prudential Plaza Two Prudential Plaza Aon Center Blue Cross and Blue Shield Tower 340 on the Park Park Tower Olympia Centre 900 North Michigan John Hancock Center Water Tower Place Harbor Point The Parkshore North Pier Apartments Lake Point Tower Jay Pritzker Pavilion Buckingham Fountain Lake Michigan Lake Michigan Lake MichiganThe skyline of a city with many large skyscrapers; in the foreground are a green park and a lake with many sailboats moored on it. Over 30 of the skyscrapers and some park features are labeled.

Figures and statistics

  • The top of Willis Tower is the highest point in Illinois. The tip of its highest antenna is 1,730 feet (527.3 m) above street level or 2,325 feet (709 m) above sea level, its roof is 1,450 feet 7 inches (442.14 m) above street level or 2,046 feet (624 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 (594 m) above sea level, the Franklin Street entrance is 595 feet (181 m) above sea level. (The highest natural point in Illinois is the Charles Mound, at 1,235 feet (376 m) above sea level.)
  • The building leans about 4 inches (10 cm) towards the west due to its slightly asymmetrical design, placing unequal loads on its foundation.[citation needed]
  • 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 (23 m × 23 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.[65]
  • The restrooms on the 103rd floor, at 1,353 feet (412 m) high, are the highest (relative to street level) in the Western Hemisphere.[66]
  • The design was inspired by an advertisement for a package of cigarettes.[67]
  • 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 feet 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 1,348 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 1,380 feet to the 103rd floor.

Broadcasting

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.

Radio stations

East mast
  • 482 m:
    • WLIT FM 93.9 MHz main, 4.0 kW, AMFM
    • WNUA FM 95.5 backup, 3.1 kW, AMFM
  • 480 m: WJMK FM 104.3 main, 4.1 kW, CBS Radio
  • 476 m: WTMX FM 101.9 main, 4.2 kW, Hubbard
  • 474 m: WBBM FM 96.3 main, 4.2 kW, CBS Radio
  • 472 m:
    • WKSC FM 103.5 main, 4.3 kW, AMFM
    • WGCI FM 107.5 main, 3.7 kW, AMFM
  • 470 m: WFMT FM 98.7, 6.0 kW
  • 468 m: WLS FM 94.7 main, 4.4 kW
  • FCC query[68]
West mast

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.

Television stations

East mast
  • 515 m:
    • WLS-TV 7 analog, 55 kW, Disney-ABC (Analog Broadcast discontinued as of June 12, 2009. Now broadcasting only in digital.)
    • WLS-TV 7 permanent digital, 4.75 kW
  • 510 m:
    • WCPX-TV 43 digital, 200 kW, Paxson
    • WCPX-TV 38 analog, 3630 kW, Paxson (Analog Broadcast discontinued as of June 12, 2009. Now broadcasting only in digital.)
    • WJYS TV 36 digital, 145 kW, Jovon Broadcasting
    • WCIU-TV 27 digital, 15.1 kW, Weigel Broadcasting
  • 509 m:
    • WXFT-TV 59 temporary digital, 200 kW, Telefutura, Univision Communications
    • WXFT-TV 50 permanent digital, 230 kW, TeleFutura
  • 498 m:
    • WTTW TV 11 analog, 60.3 kW, Window To the World Comm. (Analog Broadcast discontinued as of June 12, 2009. Now broadcasting only in digital.)
    • WBBM-TV 12 digital, 8 kW, CBS
  • 480 m:
    • WFLD TV 31 digital backup, 475 kW, Fox TV
    • WPWR-TV 51 digital backup, 508 kW, Fox TV
  • 478 m: WGN-TV 19 digital backup, 310/229 kW, Continental Broadcasting
  • 474 m:
    • WTTW TV 47 digital backup, 150 kW, Window To the World Comm.
    • WLS-TV 52 digital backup, 220 kW, WLS TV
  • unknown: WESV-LD 40 digital, 37.2 kW, Trinity Broadcasting Network
  • FCC query[70]
West mast
  • 523 m: WPWR-TV 51 digital, 1000 kW, Fox TV
  • 514 m, WLS-TV 52 temporary digital, 153.6 kW, WLS
  • 508 m, WMAQ-TV 29 digital, 350 kW, NBC/Telemundo
  • 494 m:
    • WMAQ-TV 5 analog, 20 kW (Analog Broadcast discontinued as of June 12, 2009. Now broadcasting only in digital.)
    • WPWR-TV 50 analog, 5000 kW (Analog Broadcast discontinued as of June 12, 2009. Now broadcasting only in digital.)
    • WXFT-TV 60 analog, 5000 kW, TeleFutura (Analog Broadcast discontinued as of June 12, 2009. Now broadcasting only in digital.)
  • 475 m: WFLD TV 31 digital, 690/1000 kW, Fox TV
  • 473 m: WCIU-TV 26 analog, 5000 kW (Analog Broadcast discontinued as of June 12, 2009. Now broadcasting only in digital.)
  • 472 m:
    • WCIU-TV 27 digital, 590 kW, WCIU-TV
    • WSNS-TV 44 analog 5000 kW, NBC Telemundo (Analog Broadcast discontinued as of June 12, 2009. Now broadcasting only in digital.)
    • WSNS-TV 45 digital 467/665 kW, NBC Telemundo
  • 465 m: WTTW TV 47 digital, 300 kW, Window To the World Comm.
  • 455 m: WJYS TV 36 digital, 50 kW, Jovon Broadcasting
  • 453 m: WGN-TV 19 digital, 645 kW, Continental Broadcasting
  • unknown:
    • WWME-LD 39 digital, 4.4 kW, Ch. 23 Ltd.
    • WEDE-CD 34 digital, 50 kW, First United
    • WMEU-CA 48 analog STA, 150 kW, Weigel Broadcasting
    • WMEU-LD 32 digital, 15 kW
  • FCC query[71]

Gallery

See also

References

  1. ^ a b c d e f g "Willis Tower - The Skyscraper Center". Council on Tall Buildings and Urban Habitat. 
  2. ^ a b 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
  3. ^ a b [1][dead link]
  4. ^ Snyder, Brett (16 December 2013). "A Day with United Management: Elite Status, Mileage Devaluation, and Increasing Change Fees". The Cranky Flier. Retrieved 18 December 2013. 
  5. ^ Kerch, Steve (October 20, 1991). "This job is a tall order Sears Tower project is the height of redevelopment." Chicago Tribune.
  6. ^ Arnstein & Lehr, The First 120 Years
  7. ^ Chicago Tribune, December 28, 2003.
  8. ^ Chicago Tribune, January 4, 1971.
  9. ^ "The Tallest Skyscraper", Time, Jun 11, 1973
  10. ^ Engineering Legends: Great American Civil Engineers. Books.google.com. Retrieved 2014-02-25. 
  11. ^ Lynn S.Beadle pays tribute to Khan. Books.google.com. Retrieved 2014-08-26. 
  12. ^ "Burj Dubai: The new pinnacle of vanity". Telegraph. Retrieved 2014-02-25. 
  13. ^ "Top 10 world's tallest steel buildings". Constructionweekonline.com. Retrieved 2014-02-25. 
  14. ^ "Fazlur Khan Sculpture". SEAOI. Retrieved 2014-02-25. 
  15. ^ "Databank: Sears Tower", Wonders of the World, PBS Databank. Retrieved November 19, 2007.
  16. ^ Consumer Price Index (estimate) 1800–2014. Federal Reserve Bank of Minneapolis. Retrieved February 27, 2014.
  17. ^ The Times-News, Feb 15 1975
  18. ^ SkyscraperPage – Sears Tower. Federal Communications Commission, CTBUH
  19. ^ Chicago Tribune, April 9, 1972 and Chicago Tribune, May 7, 1972.
  20. ^ Chicago Tribune, May 18, 1972.
  21. ^ Chicago Tribune, June 10, 1972.
  22. ^ Chicago Tribune, June 13, 1972.
  23. ^ Chicago Tribune, July 1, 1972.
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External links

Records
Preceded by
One World Trade Center (1970)
Tallest building in the world
442 m

1973–1998
Succeeded by
Petronas Towers
World's tallest building architectural element
442 m

1973–1998
Building with the most floors
108 floors

2001–2007
Succeeded by
Burj Khalifa
World's tallest building rooftop
442 m

1973–2003
Succeeded by
Taipei 101
Tallest building in the United States
442 m

1973–2013
Succeeded by
One World Trade Center (2006)
Preceded by
Aon Center
Tallest building in Chicago
442 m

1973–present
Incumbent