High Quality Content by WIKIPEDIA articles! The Aon Center (200 East Randolph Street, formerly Amoco Building) is a modern skyscraper in the Chicago Loop, Chicago, Illinois, United States, designed by architect firms Edward Durell Stone and The Perkins and Will partnership, and completed in 1973 as the Standard Oil Building. With 83 floors and a height of 1,136 feet (346 m), it is the third tallest building in Chicago, surpassed in height by the Willis Tower and the Trump International Hotel and Tower. The building is managed by Jones Lang LaSalle. Aon has the headquarters of the Aon Corporation, and it formerly had the headquarters of Amoco. The Aon Center is almost identical in design and floorplan to First Canadian Place in Toronto, Canada, the only major design difference being the orientation of the exterior windows.