The East Side of St. Louis Strip Clubs (Sauget, Brooklyn, Centerville, Emerson Park, IL ect...) you have to be 21. The best ones are Larry Flints Hustler Club, Penthouse, Hollywood, PT's, Diamond, Roxys, Pink Slip, and on and on.
I know that in Springfield IL, there is a strip club called Dejavu and you only have to be 18 because they do not serve liquor on the property.