Chicago appears to be the frontrunner to secure the 2016 Olympics as the four candidate cities submit bid details to the International Olympic Committee.
Madrid, Tokyo and Rio de Janeiro are the other candidates, with the final vote set for Copenhagen on October 2nd.
The United States has not hosted the Games since 1996 and President Barack Obama supports his home city's bid.
An IOC evaluation report last year ranked Tokyo and Madrid higher than Chicago, with Rio in fourth place.
Japan is also bidding for the 2015 Rugby World Cup and football's World Cup in either 2018 or 2022.