Aon Center

The Aon Center is an 83-floor office tower in the East Loop neighborhood of Chicago, reaching a total height of 346 meters. The building has a light granite exterior and occupies a full block at the corner of East Randolph Street and North Columbus Drive.

The tower opened in 1973 as the headquarters of Standard Oil Company and briefly held the title of tallest building in the world outside New York. In the early 1990s, the entire exterior was reclad with granite after the original marble facing developed cracks.

The tower's name changed with its tenants, from Standard Oil through Amoco to the current insurance firm, reflecting the shifting anchors of Chicago's financial district. Its white granite facade has become a familiar landmark for commuters and visitors navigating the office towers of the Loop today.

Public access to the building is from East Randolph Street, where the main entrance to the underground walkway system is also located. Visitors can use the connections in the base to reach other buildings in the Loop without facing outdoor weather conditions.

The reclad with over 43,000 granite panels in the 1990s was the largest project of its kind worldwide and took several years to complete. During the work, the building remained fully operational, with thousands of office workers continuing their daily routines on the floors above.

Location: Chicago

Inception: 1973

Architects: Edward Durell Stone

Official opening: 1973

Architectural style: modern architecture

Floors above the ground: 83

Floors below the ground: 5

Elevators: 50

Height: 69.8 m

Address: East Randolph St. 200, Chicago, Illinois, USA

GPS coordinates: 41.88528,-87.62139

Latest update: December 12, 2025 17:42