Chicago Architecture Info

The Aon Center





  • Amoco Building
  • Standard Oil Building
Address 200 East Randolph Street, Chicago, Illinois 60601
Neighborhood The Loop
Built 1970 - 1972
Architecture firms
  • Edward Durell Stone & Associates
  • Perkins and Will
  • Edward Durell Stone
  • Office
  • Retail
  • Skyscraper
  • Above street level: 83
  • Below street level: 5
Maximum height 1,136 feet
Cost $120,000,000
Rentable floor space 2,700,000 square feet


  • At the time of its completion, this was the tallest building in Chicago.
  • At the time of its completion, this was the fourth-tallest building in the world.
  • At the time of its completion, this was the worldʼs tallest building clad in marble. The marble wasnʼt suitable for Chicago winters and was replaced with North Carolina granite in the 1990ʼs.
  • The buildingʼs original marble facade was from Carrara, Italy; and the same Italian quarry used by Michaelangelo for his masterpiece “David.”
  • This building is connected to the cityʼs underground pedestrian tunnel system.
  • This was one of the filming locations for the 2011 movie Transformers 3.
  • A number of rabbits make their homes in the decorative planters that surround this building. They are most visible when they come out at night to eat in peace.
  • The sculpture made up of hundreds of rods sticking out of the ground is called “Untitled Sounding Sculpture,” and was made by Harra Bertoia. The rods are 19 feet tall and make an especially eerie sound when the wind blows through them at night.
  • If you stand in the right places, you can see a large, white pill-shaped object on the roof of this building. It is the transmitter for radio station WDRV/Chicago. It is 1,214 feet above ground level.
  • This is one of the few buildings in Chicago with double-decker elevators.
  • “[The] worst thing that has happened to Chicagoʼs skyline in the last 30 years.” —Paul Gapp, Chicago Tribune architecture critic, 1974


1972 Construction finished.
1973 The Sears Tower surpasseed this building as the tallest building in Chicago.
1974 A slab of the marble facade came off of this the building and plunged through the roof of the Prudential Center Annex.
1989 - 1992 All 43,000 marble panels comprising the buildingʼs facade were replaced with granite from North Carolina. The Italian marble panels were buckling and coming loose because of the harsh Chicago winters.
November, 1992 A routine inspection found that two steel columns in the buildingʼs lobby had to be reinforced. The Chicago Tribune reported that although building officials said there is no danger, additional steel plates were welded to the columns in question.
January 1, 2001 This buildingʼs name was changed from The Amoco Building to The Aon Center.
March, 2007 A plan emerged to convert the top 13 stories of this tower to residential apartments or condominiums.
May 31, 2009 A transmitter for WDRV radio was added to the roof of this building. Because of its size and placement, it was very visible to people below.
September, 2010 This building was named #20 on Chicago Magazineʼs list of the Top 40 Buildings in Chicago.
2016 Plans were floated to add an observation deck to this buidling.
2018 Plans filed with the city show that the architectural height of this building would change to 1,170 feet and six inches if the rooftop amuseument ride was built. The elevator to that ride would top out at 1,184 feet, 2½ inches. In addition, the renovation for the observatory and thrill ride would add another floor to the building, labeled 82.5. That would change the total number of floors in this building to 84.
2019 The City of Chicago approved plans to convert the 83rd floor of this building into an observatory, to add a thrill ride to its roof, and construction an 83-story glass elevator on the northwest corner of the building. It was desinged by SCB with an estimated price tag of $185,000,000.
June, 2020 The Chicago Tribune reported that plans for the 83rd-floor observatory were put on hold because of the COVID-19 pandemic.
2021 The plaza on the south side of this building was renovated, removing its central fountain and the elevator connecting to Upper East Randolph Street.


Well known in Chicagoland, but not so well known elsewhere, the Aon Center is the quiet, dignified supertall in the Chicago skyline. It lacks the flashy spires and angles of its neighbors, and instead goes for vertical stripes to add extra visual height to its already impressive stature.

From a distance, the building gives the impression of another boring grey 1970ʼs stone block. But to really appreciate the Aon Center, you have to walk right up to it and crane your neck to see the top.

Height and location give the Aon Centerʼs tenants remarkable views in all directions. People facing south look over Grant Park. People with west-facing windows can look at The Loop. People with eastern exposures are treated to Lake Michigan sunrises and boating activities. And people on the northern face get to look up the Magnificent Mile and the Chicago coastline.

But the news hasnʼt always been bright for the Aon Center. In fact, it has been routinely maligned in the print media. At first, critics called the buildingʼs design bland and uninspired. Later, things started going wrong with the building. Most famously, just after the it was completed, its much ballyhooed marble facade began to buckle. Stainless steel straps had to be wrapped around the building to keep any large chunks from falling off.

The marble facade was replaced with white granite at a cost of $60,000,000 — half what it cost to build the tower in the first place. That left the owners with 5,900 tons of unwanted marble. Some was turned into trinkets like paperweights. Some was given to a company that makes trophies. A lot was used in landscaping at Governors State University, and at Amoco facilities across the nation.