The birth of the NFL could be said to have begun as early as 1876, when the first American Rules for football were written, but the league as we now know it was truly born from the marriage of two professional sports organizations. The first incarnation of the NFL was born in 1922, when the American Professional Football Association changed their name. In 1945 the NFL had new competition, in the form of the All American Football Conference.
Over the years, the two competitive leagues would vie for dominance of the American football audience, sometimes with a good amount of animosity displayed on both sides. At one point the American Professional Football Association, having changed its name to the American Football League, sued the National Football League in court, citing anti-trust laws, claiming the NFL had an unfair monopoly on the game and thus, the business of the game.
In the end, and in hindsight, seemingly inevitably, the two organizations merged to become one league, keeping the name of the NFL, but separating the two leagues into competing conferences: the National Football Conference, or NFC and the American Football Conference, or AFC. From these two conferences, the rivalry was harnessed to produce a tremendous competition, which would be funneled toward the ultimate goal; the Super Bowl, where only one conference and one team would claim to be the best of the best.
From these not-so-humble beginnings came perhaps the most intense sporting exhibition in American history. NFL games, numbering approximately 16 games a week, regularly pull fans in excess of 50,000 into stadiums across the country. The shear size of such an audience is rivaled only by European soccer events or major world sporting events such as the Olympics. These numbers are further dwarfed by the number fans who view the games broadcast on television.