The NFL has 32 teams. They are divided into two conferences of 16. However, unlike other sports, the conferences are not split by geography. The NBA has an Eastern and Western Conference. The NFL has the American Football Conference and National Football Conference, their roots go back to when there were two different leagues.
AFL and NFL
The modern NFC can trace its roots back to 1920. The then Racine Cardinals and Decatur Staleys were two of the league's founding members. Today, those teams still exist as the Arizona Cardinals and Chicago Bears. This league continued in operation as rival leagues fell by the wayside.
But in 1959, businessman Lamar Hunt announced the formation of a new league, the American Football League. Hunt had tried to buy into the NFL, but league members rejected his bids.
In 1960, the inaugural AFL season started with the following teams: the Boston Patriots, New York Titans, Buffalo Bills, Oakland Raiders, Denver Broncos, LA Chargers, Dallas Texans, and Houston Oilers were the founding members.
The AFL proved wildly popular with its fast-paced play and different regulations. For the first time, the NFL had legitimate competition.
AFL - NFL World Championship Game
As both leagues continued to grow, fans and pundits clamoured to crown one single champion. This was a forerunner to the modern-day Super Bowl. The NFL's Green Bay Packers defeated the AFL's Kansas City Chiefs. The Packers did it again the following year before the AFL's New York Jets stunned the world and were the AFL's first world champions.
At this point, as the AFL's popularity started to overtake the NFL's, the NFL opened discussions for a league merger. Fearful of Raiders owner Al Davis, the NFL sought to protect themselves from potentially going out of business.
The Merger
The two leagues merged in 1970. The AFL teams joined the Pittsburgh Steelers, Cleveland Browns and Baltimore Colts. Together, they formed the American Football Conference. The existing NFL teams like the Packers, New York Giants, Chicago Bears and San Francisco 49ers made up the National Football Conference.
And that is why the NFL comprises two distinct conferences not based on geography—two rival leagues combined to create one super league. Twenty-six teams competed under the NFL banner in the first post-merger season, with the Baltimore Colts emerging as Super Bowl champions.
Modern times
Nowadays, both conferences have 16 teams. Many of these teams still play in the same conference they did in 1970. The NFL has added expansion teams or relocated specific teams but has yet to have a team switch conference. For example, the Oakland Raiders were a founding AFL member; they are now the Las Vegas Raiders and still play in the AFC.
The winners of each conference play in the Super Bowl, determining that season's NFL champions.