I think that you have to pay an amount but if your a member you pay less but I'm pretty sure its not free.
They do have free days however it is for Illinois residents only, the have to present a valid ID and i think there is a $3 processing fee. You can check out the aquarium's website for those free days.
I am not sure
It was free to Illinois residents on the 18th. Any other day there is a fee. The website notes all pricing.
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