<P> Throughout its history, the National Football League (NFL) and other rival American football leagues have used several different formats to determine their league champions, including a period of inter-league matchups determining a true national champion . </P> <P> Following its founding in 1920, the NFL first determined champions through end - of - season standings, but switched to a playoff system in 1933 . The rival All - America Football Conference (AAFC) and American Football League (AFL) have since merged with the NFL (the only two AAFC teams that currently exist joined the NFL in 1950--the Cleveland Browns and the San Francisco 49ers), but AAFC championship games and records are not included in NFL record books . The AFL began play in 1960 and, like its rival league, used a playoff system to determine its champion . </P> <P> From 1966--1969 prior to the merger in 1970, the NFL and the AFL agreed to hold an ultimate championship game, first called the AFL - NFL World Championship Game and later renamed the Super Bowl after 1968 . Following the merger in 1970, the Super Bowl name continued as the game to determine the NFL champion . The most important factor of the merger was that all ten AFL teams joined the NFL in 1970 and every AFL championship game and record is included in NFL record books . The old NFL Championship Game became the NFC Championship Game, while the old AFL Championship Game became the AFC Championship Game . The NFL lists the old AFL / NFL championship games with "new" AFC / NFC championship games in its record books . The Green Bay Packers have won the most championships with 13 total (9 NFL championships pre-merger, four (4) Super Bowl championships). The Packers are also the only team to win three consecutive championships, having done so twice (1929--1931, 1965--1967). The Chicago Bears have won the second most overall championships with nine (9) (eight NFL championships, one Super Bowl championship). </P> <P> At its inception in 1920, the NFL had no playoff system or championship game: the champion was the team with the best record during the season as determined by winning percentage, with ties omitted . This sometimes led to very unusual results, as teams played anywhere from six to twenty league games in a season, and not all teams played the same number of games or against league talent . </P>

Who won the most national championships in football