In order to equalize the number of teams in each conference, three NFL teams that predated the AFL's launch (the Cleveland Browns, Pittsburgh Steelers, and the then-Baltimore Colts) joined the ten former AFL teams to form the AFC. The two AFL divisions AFL East and AFL West were more or less intact, while the NFL's Century Division, in which the Browns and the Steelers had played since 1967, was moved from the NFL to become the new AFC Central.
To balance the number of squads in each conference, three NFL teams that existed before the AFL's inception (the Cleveland Browns, Pittsburgh Steelers, and the then-Baltimore Colts) joined the ten former AFL teams to establish the AFC. The two AFL divisions AFL East and AFL West remained largely unchanged, while the NFL's Century Division, in which the Browns and the Steelers had competed since 1967, was transferred from the NFL to become the new AFC Central.