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Aon Center (Chicago)

Coordinates: 41°53′07″N 87°37′17″W / 41.88528°N 87.62139°W / 41.88528; -87.62139
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Aon Center
The Aon Center, designed by Edward Durell Stone
Aon Center (Chicago) is located in Chicago metropolitan area
Aon Center (Chicago)
Location within Chicago metropolitan area
Aon Center (Chicago) is located in Illinois
Aon Center (Chicago)
Aon Center (Chicago) (Illinois)
Aon Center (Chicago) is located in the United States
Aon Center (Chicago)
Aon Center (Chicago) (the United States)
General information
Architectural styleModern
Location200 E. Randolph St.
Chicago, Illinois 60601
United States
Coordinates41°53′07″N 87°37′17″W / 41.88528°N 87.62139°W / 41.88528; -87.62139
Construction started1970
CostUS$120 million
OwnerMark Karasick
Victor Gerstein[1]
Architectural346.3 m (1,136 ft)[2]
Tip362.5 m (1,189 ft)[2]
Top floor328 m (1,076 ft)[2]
Technical details
Floor count83 above ground[2]
5 below ground
Floor area334,448 m2 (3,599,968 sq ft)[2]
Lifts/elevators50, made by the Otis Elevator Company
Design and construction
Architect(s)Edward Durell Stone[2]
DeveloperStandard Oil of Indiana
Main contractorTurner Construction[2]

The Aon Center (200 East Randolph Street, formerly Amoco Building)[3] is a modern super tall skyscraper east of the Chicago Loop, Chicago, Illinois, United States, designed by architect firms Edward Durell Stone and The Perkins and Will partnership, and completed in 1973[4] as the Standard Oil Building (nicknamed "Big Stan").[5] With 83 floors and a height of 1,136 feet (346 m), it is the fourth-tallest building in Chicago,[2] surpassed in height by Willis Tower, Trump International Hotel and Tower, and St Regis Chicago.

The building is managed by Jones Lang LaSalle, which is also headquartered in the building. Aon Center also houses the headquarters of Aon and one of Kraft Heinz's two headquarters (the other being in Pittsburgh), and the former world headquarters of Amoco prior to its merger into BP.[6][7][8][9]

The building was briefly the tallest in Chicago, but was soon surpassed by the Sears Tower. It was the fourth-tallest building in the world at the time of its completion.



View from Buckingham Fountain of the building while it was under-construction

The Standard Oil Building was constructed as the headquarters of the Standard Oil Company of Indiana. Standard's previous home had been 910 S. Michigan Avenue. This building was constructed in 1911 by the Karpen Brothers Furniture Company and was purchased by Standard in 1927. When the new Standard Oil Building was completed in 1973, it was the tallest completed building in Chicago and the fourth-tallest in the world, earning it the nickname "Big Stan".[10] In 1974, the taller Sears Tower (now Willis Tower) in Chicago surpassed it as the tallest completed building in Chicago (the Sears Tower was also the tallest in the world). However, the Sears Tower had already been topped out in May 1973.[11][12] When the Aon Center opened as the fourth-tallest completed building in the world, it was only exceeded in height by the twin towers of the original World Trade Center and the Empire State Building in New York City.[11] Originally clad in marble, the Aon Center was also the tallest marble-clad building in the world.[12]

The building employs a tubular steel-framed structural system with V-shaped perimeter columns to resist earthquakes, reduce sway, minimize column bending, and maximize column-free space. This construction method was also used for the original World Trade Center twin towers in New York City.


Aon Center in the 1990s during its refacing, with temporary work elevators erected in the building's corners

When completed, it was the world's tallest marble-clad building, sheathed entirely with 43,000 slabs of Italian Carrara marble. The marble used was thinner than previously attempted in cladding a building, which soon proved to be a mistake. On December 25, 1973, during construction a 350-pound marble slab detached from the façade and penetrated the roof of the nearby Prudential Center.[13] In 1985, inspection found numerous cracks and bowing in the marble cladding of the building. To alleviate the problem, stainless steel straps were added to hold the marble in place.[10] Later, from 1990 to 1992, the entire building was refaced with Mount Airy white granite at an estimated cost of over $80 million.[5][14] Amoco was reluctant to divulge the actual amount, but it was well over half the original price of the building, without adjustment for inflation. Two-thirds of the discarded marble was crushed and used as landscaping decoration at Amoco's refinery in Whiting, Indiana, one-sixth was donated to Governors State University, in University Park, and one-sixth donated to Regalo, a division of Lashcon Inc. Under a grant from the Illinois Department of Rehabilitative Services, Regalo's 25 handicapped workers carved the discarded marble into a variety of specialty items such as corporate gifts and mementos including desk clocks and pen holders.[5][15] The building's facade somewhat resembles that of the North and South tower of the former World Trade Center Complex due to the upward flow of the columns.


The Standard Oil Building was renamed the Amoco Building when the company changed names in 1985. In 1998, Amoco sold the building to The Blackstone Group for an undisclosed amount, estimated to be between $430 and $440 million.[5][10] It was renamed as the Aon Center on December 30, 1999, although the Aon Corporation would not become the building's primary tenant until September 2001.[16] In May 2003, Wells Real Estate Investment Trust, Inc. acquired the building for between $465 and $475 million.[5][17] On August 10, 2007, Wells Real Estate Investment Trust, Inc. changed its name to Piedmont Office Realty Trust, Inc.)[18]

Real estate investors Mark Karasick and Victor Gerstein acquired the building from Piedmont in 2015 for $713 million.[1]

Planned observation deck[edit]

On May 14, 2018, the building's owners unveiled a $185 million proposal for an observatory featuring a thrill ride on the roof called the Sky Summit, the world's tallest exterior elevator, and new entrance pavilion. The observatory was supposed to be completed in 2022, but the COVID-19 pandemic had been announced to have delayed construction plans by about a year.[19][20]

Position in Chicago's skyline[edit]

The skyline of a city with many large skyscrapers; in the foreground is a green park and a lake with many sailboats moored on it. Over 30 of the skyscrapers and some park features are labeled.311 South WackerWillis TowerChicago Board of Trade Building111 South WackerAT&T Corporate CenterKluczynski Federal Building333 South WabashChase TowerThree First National PlazaMid-Continental PlazaRichard J. Daley CenterChicago Title and Trust Center77 West WackerPittsfield BuildingLeo Burnett BuildingThe Heritage at Millennium ParkCrain Communications BuildingIBM PlazaOne Prudential PlazaTwo Prudential PlazaAon CenterBlue Cross and Blue Shield Tower340 on the ParkPark TowerOlympia Centre900 North Michigan875 North Michigan AvenueWater Tower PlaceHarbor PointThe ParkshoreNorth Pier ApartmentsLake Point TowerJay Pritzker PavilionBuckingham FountainLake MichiganLake MichiganLake Michigan


See also[edit]


  1. ^ a b Cunningham, Cathy; Grossman, Matt (June 8, 2018). "J.P. Morgan, Brookfield Provide $678M Financing Package for Chicago's Aon Center". Commercial Observer.
  2. ^ a b c d e f g h i "The Skyscraper Center: Aon Center". Council on Tall Buildings and Urban Habitat. Archived from the original on August 8, 2014.
  3. ^ Roeder, David (February 21, 2003). "New owner expected for Aon Center". Chicago Sun-Times. Retrieved September 18, 2008 – via Newsbank.
  4. ^ Saliga, Pauline, ed. (1990). The Sky's the Limit: A Century of Chicago Skyscrapers. New York: Rizzoli. p. 219. ISBN 978-0847811793.
  5. ^ a b c d e "Aon Center, Chicago". Emporis. Archived from the original on December 7, 2006. Retrieved April 23, 2008.
  6. ^ Tadena, Nathalie; Dean, Jason; Scism, Leslie (January 14, 2012). "Aon Shifts Headquarters to London". The Wall Street Journal. Archived from the original on August 31, 2017. Retrieved January 20, 2020.
  7. ^ "Contacts". Amoco. February 12, 1998. Retrieved on March 31, 2010.
  8. ^ Du, Lisa (February 23, 2017). "Kraft Heinz eliminated another 1,000 jobs in 2016". Chicago Tribune. Bloomberg News.
  9. ^ "Kraft Heinz preps HQ move into Chicago". Chicago Business Journal. July 15, 2015. Retrieved January 20, 2020.
  10. ^ a b c "Aon Center". Glass Steel and Stone. Archived from the original on August 26, 2007. Retrieved September 25, 2007.
  11. ^ a b Nelson, Bryce (May 7, 1973). "Sears 'Topping Out' Puts Chicago On Top". Newspapers.com. Retrieved October 9, 2022.
  12. ^ a b "1973 – Aon Center, Chicago, Illinois". Archiseek - Irish Architecture. September 20, 2009. Retrieved October 9, 2022.
  13. ^ Chicago Tribune, December 26, 1973
  14. ^ McMillan, Greg (June 12, 2007). "Two buildings, two cities, one problem". The Globe and Mail. Toronto. Retrieved September 25, 2007.
  15. ^ Cosper, Stephen D.; William H. Hallenbeck; Gary R. Brenniman (January 1993). "Construction and Demolition Waste: Generation, Regulation, Practices, Processing, and Policies" (PDF). University of Illinois at Chicago, Office of Solid Waste Management. p. 31. Archived (PDF) from the original on October 9, 2022. Retrieved March 26, 2010.
  16. ^ McManus, David (July 12, 2018). "AON Center Chicago: Skyscraper Architecture". e-Architect. Retrieved January 20, 2020.
  17. ^ "Trophy Building Sale Sets New Record". Miller Cicero, LLC. October 7, 2003. Archived from the original on May 18, 2007. Retrieved September 25, 2007.
  18. ^ "Wells REIT Changes Name to Piedmont Office Realty Trust". Piedmont Office Realty Trust, Inc. Archived from the original on June 10, 2008. Retrieved August 10, 2007.
  19. ^ Marotti, Ally; Kamin, Blair (May 15, 2018). "Aon Center's planned observation deck, Chicago's third, could create competition for tourist dollars". Chicago Tribune. Retrieved January 20, 2020.
  20. ^ "Construction halted for Aon Center observatory in Chicago due to coronavirus pandemic". USA TODAY. Retrieved November 28, 2020.

External links[edit]

Preceded by Tallest building in Chicago
1,136 ft
Succeeded by
Tallest building in the United States outside of New York City
1,136 ft