Hundreds of cyclists gathered in the plaza for a free continental breakfast and t-shirts.
This is the 22nd year the city has held the event, which is part of Chicago's commitment to become a more bicycle-friendly city.
"Yes, I want to make the City of Chicago the most bike-friendly city in America.
We are building more protected bike lanes, we've moved from 10th to 5th, 20 percent of the entire protected bike lanes in America are in the City of Chicago," said Mayor Rahm Emanuel.
On Thursday, the city opened new protected bike lanes on the busiest cycling area, on Milwaukee Avenue between Kinzie and Elston. It is part of Emanuel's plan to build 100 bike lanes across the city.
