Facts

• During the groundbreaking ceremony on April 6, 1970, a helicopter hovered 1,136 feet (346 m) over the site to demonstrate how tall the building would be.
• Until the Shanghai World Financial Center was topped out in 2007, this was the tallest building in the world without any major antennae, spires, or finials at the top. In July 2009 a small communications antenna was installed on the roof.
• From 1990 to 1992 the building's 43,000 marble cladding panels were replaced by two-inch-thick Mt. Airy granite panels at a cost of about $80 million.
• Marble removed from the cladding of the building was crushed and used as decorative stone surrounding the Amoco refinery inWhiting, Indiana. The project was referred to as the "Whiting Beautification Project".
• Wells Real Estate Investment Trust, Inc. acquired Aon Center from The Blackstone Group for $475 million during the week ending May 10th 2003.
• This was the tallest building in Chicago from 1973 until 1974, when it was surpassed by the Willis Tower.