In the United States, gridiron-based variants of the game did not distinguish themselves from existing codes until 1871, when Harvard University began playing a variation known as the "Boston Game." This allowed a player to pick up the ball and run with it if he were chased and it quickly spread, with innovations added by Yale University student Walter Camp. The oldest existing non-university semiprofessional football club is the Watertown Red & Black, which was founded in 1896. The Arizona Cardinals, formed in Chicago in 1898, are the oldest team in the National Football League.