The All-America Football Conference (AAFC) was a professional American football league that challenged the established National Football League (NFL) from 1946 to 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: San Francisco 49ers, Cleveland Browns and Baltimore Colts (not related to the later NFL team that would play in Baltimore from 1953 through 1983, now the Indianapolis Colts).