Aon Center, Modern skyscraper in East Loop, Chicago, United States
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.
Completed in 1973 as the Standard Oil Building, the tower was then the fourth-tallest in the world, behind only the World Trade Center towers and the Empire State Building. It was briefly Chicago's tallest until the Sears Tower overtook it in 1974. Originally clad in 43,000 Carrara marble slabs, it was refaced with Mount Airy white granite between 1990 and 1992 after the marble cracked.
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.
The Aon Center has no public facilities for visitors, unlike the Willis Tower or the John Hancock Center; the 83 floors are used only for offices. The building stands at 200 East Randolph Street in the Chicago Loop, and its entrance is reached from that street.
The original Carrara marble cladding failed: on December 25, 1973, a 350-pound slab fell and pierced the roof of the nearby Prudential Center. Two-thirds of the discarded marble was crushed and used as landscaping at Amoco's Whiting, Indiana refinery; the rest went to Governors State University and to Regalo, where 25 workers with disabilities carved it into desk clocks and pen holders.
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