It's been nearly 60 years since the Kansas City Chiefs and Green Bay Packers met in the first AFL-NFL world championship game — retroactively known as Super Bowl I. At the time, it was billed by some as a "supergame" between the rival NFL and AFL leagues.
The AFL was the most significant of many upstart leagues that materialized to challenge the NFL's dominance of the sport starting in 1960. By the end of the decade, the two leagues had an agreement in place to merge starting in the 1970 season. They became the NFC and AFC, and the annual "supergame" would take place between the champions of each conference.