What were there back in the good old days ... 3, maybe 4 teams? ;o)
The precursor to the NFL, the American Professional Football Association, was formed in 1920 with 14 teams from the Midwest and New York. The champions that first season were the Akron Pros, who finished undefeated. Included in that first season were the Chicago Staleys, later renamed the Chicago Bears.
In 1921, the Association expanded to 22 teams, including the Green Bay Packers. The Packers were organized in 1919, but spent their first two seasons as an independent pro team before joining the NFL. Also in 1921, Staley turned his team over to George Halas. Fritz Pollard of the Akron Pros became the first black head coach. The Staleys won the championship.
In 1922, the Association changed its name to the National Football league. The Staleys became the Bears. 18 teams participated, with Canton winning the championship that year.
In 1923, in a game between the Bears and the Toledo Maroons, Halas of the Bears recovered a Jim Thorpe fumble and returned it for a 98 yard touchdown, a record which stood until 1972. Canton went undefeated again and claimed its second consecutive championship.
In 1925, the league established its first roster limit, at 16 players. Red Grange signed with the Bears. He later left over a contract dispute and joined a rival league, the brief-lived first incarnation of the AFL.
In 1927, to strengthen the financial viability of the league, it was cut from 22 down to 12 teams, including adding Grange's New York Yankees football team from the folded AFL. Grange was injured, and the NY Giants won the championship, with 10 shutouts in 13 games.
In 1929, the Green Bay Packers won their first championship in a 10 team league.
Did you know that prior to 1898, a touchdown was worth 4 points, and a field goal worth 5? The first pro player and team made up entirely of professionals came from Western Pennsylvania. The forward pass was legalized in 1906. In the same year, the Ohio League was racked by a betting scandal and inflated player salaries.
Other trivia:
The first-ever playoff game was in 1932, as the result of a tie in the standings between the Bears and the Portsmouth, OH Spartans. It was played indoors due to bitter cold and a snowstorm, and played on an 80 yard field. The goalposts were moved to the back of the end zone for the game, an innovation that the league adopted the following year for all its games. Boston was awarded a franchise, the Braves, which later became the Boston Redskins.
In 1933, the rules were changed to allow forward passes from anywhere behind the line of scrimmage. Prior to then, a pass had to be from at least 5 yards behind the line. For the first time, the league played in two divisions with a playoff for the championship. Pittsburgh's Art Rooney was awarded a franchise, the Pittsburgh Pirates. David Jones sold the Chicago Cardinals to Charles W. Bidwell, beginning the long and sorry wandering captivity of the Cardinals franchise at the hands of the Bidwell clan.
In 1934, the Portsmouth Spartans were purchased, relocated to Detroit, and renamed the Lions. A prior Detroit franchise named the Panthers had folded some years earlier. The Thanksgiving Day game between the Bears and the Lions was the first nationally broadcast NFL game.
In 1937, the Redskins moved from Boston to Washington D.C.
In 1939, the first televised game, between the Brooklyn Dodgers and the Philadelphia Eagles, for the approximately 1000 sets in New York. Total NFL attendance (for the entire league!) exceeded 1,000,000 for the first time.
In 1940, Art Rooney sold the Pittsburgh franchise and purchased a share of the Eagles. In 1941, Rooney and Bell swapped the Philadelphia franchise for the Pittsburgh team, and renamed them the Steelers. Daniel F. Reeves became co-owner of the Cleveland Rams.
In 1943, league rosters were depleted by the war effort. Helmets became manditory.
In 1944, coaching from the bench was legalized. The Steelers and Eagles fielded a joint team for that season (called the "Steagles" by fans).
In 1946, Reeves was granted permission to relocate the Rams from Cleveland to Los Angeles. The rival All-American Footbal Conference began play. The Browns of the AAFC (along with San Francisco and Baltimore) later merged with the NFL.
In 1948, a player from the Rams painted horns on his helmet, the first modern helmet emblem.
In 1952, Ted Collins sold the New York Yanks' franchise back to the NFL. A new franchise was awarded to a group in Dallas after it purchased the assets of the Yanks, January 24. The new Texans went 1-11, with the owners turning the franchise back to the league in midseason. For the last five games of the season, the commissioner's office operated the Texans as a road team, using Hershey, Pennsylvania, as a home base. At the end of the season the franchise was canceled, the last time an NFL team failed. Also, the Pittsburgh Steelers abandoned the Single-Wing for the T-formation, the last pro team to do so.
In 1956, the NFL Players Association was formed. Grabbing the facemask of a player other than the ballcarrier was made illegal.
In 1960, Dallas and Minnesota were awarded NFL franchises. The Minnesota franchise had played in the fourth incarnation of the AFL before withdrawing.
In 1961, Canton, OH, where the NFL was formed, was selected as the site of the Hall of Fame.
In 1962, facemasking of the ballcarrier was prohibited. The NFL signed a contract with CBS to broadcast all regular-season games. $4.65 Million.
In 1963, Don Shula became head coach of the Colts.
In 1966, the AFL and NFL announced their decision to merge.