The company is listed on the stock index S & P 500 that employs over 61,000 people. (February 2009)
The headquarters of the company is located in Chicago Aon Center. In Los Angeles, the company's employees working in Aon Center of the city.
Aon Corporation was created in 1982 from the merger of U.S. insurance companies Ryan Insurance Group (founded by Pat Ryan in the 1960s ) and Combined International Corporation (founded by W. Clement Stone in 1919 ).
When the terrorist attacks on 11 September 2001, 175 employees of the company in the southern tower of the World Trade Center died.
In August 2008, the company acquired the British insurance company Benfield Group in London. Subsidiaries in Germany is Aon Jauch & Huebener in Hamburg.
In October 2010, the 4.9 billion -US-dollar acquisition of Hewitt Associates has completed.
On 3 June 2009, it was announced that Aon is the successor to AIG as shirt sponsor of English football club Manchester United. The company is also title sponsor of the team Arena Motorsport in the BTCC that competes henceforth under the name Team Aon.