Major professional sports leagues in the United States and Canada
The Canadian Football League is the highest level of play in Canadian football. The league was organized in 1956 as a cooperative agreement between two regional leagues, the Big Four (which dated to 1907) and the WIFU (which was founded in 1936), and became independent from Football Canada in 1958. The league now consists of nine teams, all based in Canada. The Grey Cup is awarded annually to the champion every November and is the highest attended sporting event in the nation. The oldest extant teams, the Hamilton Tiger-Cats and the Toronto Argonauts, trace their origins to the late 1860s and early 1870s, which ranks them amongst the oldest professional sports teams of any kind still in existence on the continent. The CFL attempted an expansion into the United States in cities that had no NFL team between 1993 and 1995, though the expansion teams all either folded or relocated to Canadian cities.
National Football League
The NFL was always the foremost professional football league in the United States; it nevertheless faced a large number of rival professional leagues through the 1930s and 1940s. Rival leagues included at least three separate American Football Leagues and the All-America Football Conference (AAFC), on top of various regional leagues of varying caliber. Three NFL teams trace their histories to these rival leagues, including the Los Angeles Rams (who came from a 1936 iteration of the American Football League), the Cleveland Browns and San Francisco 49ers (the last two of which came from the AAFC). By the 1950s, the NFL had an effective monopoly on professional football in the United States; its only competition in North America was the professional Canadian football circuit, which formally became the Canadian Football League (CFL) in 1958. With Canadian football being a different football code than the American game, the CFL established a niche market in Canada and still survives as an independent league.