Admission is free to children 14 and under. Also free to Illinois residents on Thursdays 5 pm to 8 pm.
I believe 18 and under had a reduced rate on Monday when I went, so there was still a cost. Other days maybe free.
Overall, the cost of admission will always be under $30 regardless of who you are but for Illinois residents, if you present an ID, it should be around $22.
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