Sept 16-30 and then Oct 3 and 10 However those are only for residents of Illinois. If you do not have Id then you will pay. There are also other museums that have free days. This past weekend we did Shedd and observatory on the 14th because those were free but field museum wasn't free on 14 but was on 15. Need to check websites to plan best trip.
All September is free
I don t know
All September
The days left are September: 16th-30th October: 3rd and 10th
Every day in September, this month only
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