AAFC: 1946-1949 (4 seasons)
Attracted many of the best players, introduced innovations to the game, and founded Browns/49ers franchises
AFL3: 1940-1941 (2 seasons)
Created when three new franchises joined with three other teams that were lured away from the APFL
APFL: 1938-1939 (2 seasons)
Began as minor-league Midwest Football League before changing aspirations to lure teams from the previously failed AFL.
AFL2: 1936-1937 (2 seasons)
In its brief history, the league made history by being the first league to introduce "major league" football to the West Coast.
AFLG: 1926-1926 (1 season)
Also known as the Grange League, founded by the sports agent who brought along his star player: future HOFer Red Grange.
NFL: 1920- (100 seasons)
Founded in an auto showroom in Canton, Ohio, known as the American Professional Football Association (APFA) its first 2 seasons.
NYPFL: 1908-1919 (12 seasons)
The league's best team, the Jeffersons, was instrumental in bringing the NYPFL and the Ohio League together to form the NFL.
OL: 1902-1919 (18 seasons)
Informal and loose association of teams that competed for the Ohio Independent Championship (OIC).
NFL1: 1902-1902 (1 season)
Founded by baseball owners in Philadelphia, the 3-team league was comprised of baseball and football stars of the day.
WPPFC: 1890-1919 (30 seasons)
A loose association of American football amateur and pro clubs that operated until the arrival of the Ohio League and NYPFL.