Peter Ueberroth, US Olympic Committee chairman, said the decision was "very tough" and “not necessarily a landslide”.
Chicago presented a plan centreed around its lakefront. The city plans to turn a section of Grant Park into an Olympic celebration centre and it will build the Olympic village along the beach.
Chicago is reported to have presented a financial guarantee package, from both public and private sources, of more than $1 billion. Costs for building venues and operations have been estimated at $5 billion.
Patrick Ryan, chairman of the Chicago 2016 bid committee said, "it's a great day for Chicago. 2016, here we come."
Chicago is likely to face Madrid, Milan, New Delhi, Prague, Rio de Janeiro, Rome and Tokyo in the race to host the 2016 Games. The IOC will select the 2016 host in October 2009.
