The origin of professional football can be traced back to 1892, with Pudge Heffelfinger's $500 (estimated $13,246.55 in 2019 dollars) contract to play in a game for the Allegheny Athletic Association against the Pittsburgh Athletic Club. In 1920 the American Professional Football Association was formed. This league changed its name to the National Football League (NFL) two years later, and eventually became the major league of American football. Primarily a sport of Midwestern industrial towns in the United States, professional football eventually became a national phenomenon.