The National Football League was first known as the American Pro-Football Association, founded by eleven original teams located in the area of Ohio. The most recognized team were known as the Canton Bulldogs which is currently the Cleveland Browns. the first 'official' season of the association was in 1920 when the eleven small-town teams signed on a post-season championship game. However by the end of the season only 5 teams remained in the association. The great depression made it very hard for a new organization to uphold it's franchises as only a hand full of teams would make it through the whole season without folding. Due to the unstable nature of the association throughout the 1920's-30's the champions were determined through whoever had the better win-loss ratio until in 1933 an annual championship game was set into place between the best team from the two separate divisions. The American Pro Football Association would be changed later to the National Football League as small town teams from the mid-west expanded into bigger cities.
Lamar Hunt in 1960 started his own rival organization and capitalized on the aspects that the NFL lacked, showmanship, flashy attitude of the AFL. The organization soon grew financially dominant over the NFL. Some significant additions made by the AFL was the addition of a stadium game clock which allowed the fans to see the time remaining in the quarter of the game, one major difference between the AFL and NFL was that the AFL openly allowed African-American athlete's to join franchises as main positions (Middle-linebacker, Quarterback). This caused a major void of talent that the NFL lost from college drafts.
The NFL's counter in terms of franchises was the addition of the Dallas Cowboys in response to the popularity of the Dallas Texans (AFL)
Two separate organizations led to two college drafts and player salaries were varied and often scrutinized because one organization payed more than the other etc. Under state laws in the late 1960s the AFL merged into the NFL which was split into the former AFL teams, now known as the AFC and the NFC and the winners of both conferences would face each other in a championship game which was later called the Super Bowl.
In the 1970s and 1980s the NFL was one of America's most watched sports as the rule changes were geared to a more fast paced high adrenaline style which attracted the casual fan and appealed the hardcore fans. The additions were Monday Night Football was a popular attraction on television but the main show was the Superbowl, which dominated all American television records from the 70s to the present. The recent attempt to expand to Europe, known as NFL Europa features 1 game every season to be taken place in Birmingham, England as the attempts in Germany resulted in failure. The England games racked in millions of viewers.