There are many casinos throughout the US that are 18+. They are all casinos on Indian reservations or land and owned by various tribes. Michigan
has a few as does New York. The most famous is probably Foxwoods in CT. Do searches on the web for Indian casinos near you.
As a side note, a friend and I will be at Turning Stone Casino in NY next week and weekend for the Heartland Poker Tour. He will be playing in some of the preliminary events (non satelite). Is anyone else planning on being there?