Gambling is legal in the USA, but it is regulated and there are plenty of restrictions. Almost all states allow the lottery, which makes some form of gambling legal in all states.
However, casino gambling has stricter regulations. The only two states in the country that allow state-wide casino gambling are Louisiana and Nevada. Most other states limit legal casino gambling to small areas that are usually near large cities. These areas include New Jersey (Atlantic City), Mississippi (Tunica) and American Indian reservations. American Indian tribes are considered sovereign nations and are therefore allowed to operate casinos in their territories.