The All-America Football Conference (AAFC) was a professional American football league that challenged the established National Football League (NFL) from 1946–1949. One of the NFL's most formidable challengers, the AAFC attracted many of the nation's best players, and introduced many lasting innovations to the game. However, the AAFC was ultimately unable to sustain itself in competition with the NFL. Three of its teams were admitted to the NFL: the San Francisco 49ers, the Cleveland Browns and the Baltimore Colts (not directly antecedent to the later second Colts team that would play in Baltimore in the NFL from 1953 through 1983, now the Indianapolis Colts).