The Topps football card set originally covered the players of the NFL, while Fleer began producing cards representing the AFL players in 1960.
To the dismay of Topps, the NFL Players Association signed a 3-year contract with the Philadelphia Gum Co. for the right to produce football cards in 1964. The AFL took the opportunity to switch from Fleer and contract with Topps to produce their football cards.
Although the Philadelphia football cards are interesting, the quality of the cards produced never quite caught up to Topps. After the two leagues merged, Topps was the logical choice to produce the football cards for both leagues.
by Dean Hanley