The effort brings together hundreds of the world's brightest leaders on a broad spectrum of subjects. More than 25,000 people could take part.
Key speakers this year include astronaut Buzz Aldrin, activist and speaker Elizabeth Smart, chef Mario Batali, and movie director M. Night Shyamalan.
Among Monday's highlights: former Mayor Richard Daley leads a tour of the future Maggie Daley Park.
Current Mayor Rahm Emanuel also is set to lead a Divvy bike ride through the city and to talk about the program.
Monday afternoon, analysts from BuzzFeed, Cars.com, and other companies were scheduled to talk about how retailers use technology and social media to study consumers' buying habits.