Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The National Football League (NFL) is the highest level of professional American football. It was formed by eleven teams in 1920 as the American Professional Football Association, with the league changing its name to the National Football League in 1922. The league currently consists of thirty-two teams from the United States. The league is divided evenly into two conferences the American Football Conference (AFC) and National Football Conference (NFC), and each conference has four divisions that have four teams each. The NFL is organized as an unincorporated association of its 32 teams. The NFL is by far the best attended domestic sports league in the world by average attendance per game, with 67,509 fans per game in the latest regular season (2009).