 By the time football had become a professional event, playing on Thanksgiving had already become an institution.Records of pro football being played on Thanksgiving date back to as early as the 1890s, with the first pro–am team, the Allegheny Athletic Association of Pittsburgh, Pennsylvania.In 1902, the "National" Football League, a Major League Baseball-backed organization based entirely in Pennsylvania and unrelated to the current NFL, attempted to settle its championship over Thanksgiving weekend; after the game ended in a tie, eventually all three teams in the league claimed to have won the title.