The legal age to gamble in the United States varies by state. For instance, in Alabama, the minimum age for pari-mutuel betting varies by county but is typically 18 or 19. In Alaska, you must be at least 18 to play slot machines and 19 for bingo. Store-bought lottery tickets typically require the buyer to be at least 18. However, it's important to research the specific regulations for each state as they can significantly vary.