Here are the states that offer 18+ land-based gambling in some capacity:
NOTE: A question mark without a number means that form of gambling is legal in that state, but the minimum age requirements, if any, are not known. ... CLegal-Age Gambling Opportunities and Restrictions.
|Casinos and Slot Machines||21|
|Charity Bingo & Pull-tabs||18|
Markets With 18+ Sports Betting