Travel on Tuesday, Wednesday, and Saturdays from April 17 through June 26, 2018. Searching on United.com we found flights departing SFO on Saturday, May 5 and returning from ORD on Tuesday, May 8, 2018. This is a United Airlines Basic Economy fare, which limits your carry-on allowance to just one small personal item such as a purse or small backpack up to 17x10x9 inches. Consider the higher regular economy fare if you need more carry-on allowance.
See all our other fare deals from San Francisco on the SFO flight deals page here.
If you need a place to stay in Chicago her is what's available on the listed dates from Hotelwatchdog.