Hi Ed
Just like I am not sure 1952 Topps baseball cards would be considered Topps first baseball cards (1948 Topps Magic Photos; 1951 Red and Blue backs; 1951 Connie Mack All-Stars; 1951 Topps Teams) I don't know if 1956 Topps football cards would be called Topps first football cards (1950 Topps Felt Backs; 1951 Topps Magic; 1955 Topps All-American).
1956 Topps football cards are the first to feature only pro players. At only 120 cards it's an easy set to put together of course mine is in P/F/G condition. Nice big cards just like your 1952 baseball cards, and the backs are awesome. Most expensive card in the set according to my standard catalog (that is a few years old) is the #1 card Jack (John) Carson $200 NM. I like the team cards too.
I bet you complete this football set before you complete the 1952 Topps baseball set
Larry