The question of when amateur football became professional is murkier. Before various professional leagues were formed, football was played as a diversion, and as an expression of school spirit for a multitude of college teams. What we do know is when the first documented example of a person accepting money to play football for a team. Of course, it’s likely that so-called ringers were brought in to play football on amateur teams for a long time before anyone could prove they were being paid, but in November of 1892, we have the first written proof of a man being paid to play football. The Allegheny Athletic Association kept a ledger of all their income and expenses for the season, and there among the fees for park rental and the receipts for tickets sold is a line item for a $500 cash payment to William Heffelfinger to play for the Allegheny Athletic Club versus the Pittsburgh Athletic Club
Apparently, it was worth the money. Heffelfinger recovered a fumble during the game, and he returned it for the game’s only score, a touchdown that was worth four points. Even with the big cash outlay to Heffelfinger, the 4-0 win netted a $621 profit for Allegheny, and the ledger is now in the NFL Hall of Fame. It’s the Birth Certificate of pro football.