In the world of professional sports, the National Football League blitzes the competition. The organization oversees America's most popular spectator sport, acting as a trade association for 32 franchise owners. Among the league's functions, the NFL governs and promotes the game of football, sets and enforces rules, and regulates team ownership. It generates revenue mostly through marketing sponsorships, licensing merchandise, and by selling national broadcasting rights to the games. The teams operate as separate businesses but share a percentage of the league's overall revenue. Founded in 1920 as the American Professional Football Association, the league has been known as the NFL since 1922.