The ceremony began at the Copenhagen Opera House at 10 a.m.Chicago time. That's when Danish, Spanish and Japanese royalty mingled with American and Brazilian diplomats and athletes and celebrities from around the world gathered to rounded out the star-studded international event.
Michelle Obama and Oprah Winfrey will represent for the US until President Obama arrives Friday morning for the vote.
In the meantime, Chicago's Olympic bid got a boost this morning from an emotional paralympian this morning in Copenhagen.
Linda Mastandria, choked back tears as she spoke of what the movement had meant in her own life.
"I never once thought I could excel on the field of sport," she sobbed. It was at the University of Illinois, she says, that she realized, "I could be an athlete!"
"It made me view myself in a whole different way," Mastandria said.
"What this movement offers is such power. I can't believe we are 24 hours from this decision!"
All athletes are partial to competing in their home countries, and the American sports stars who gathered on Chicago's behalf were certainly no exception.
"Everyone at the Olympics has a phenomenal story," said NBA and Olympic basketball great David Robinson. "And that story will be told in Chicago".
"For us, it would be a tremendous honor to host the world!"
Check out NBCChicago's full coverage of the Olympic Bid here.