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.
Professional football (gridiron)
Indoor football has also developed in the United States, beginning with the Arena Football League, which formed in 1987. The AFL is the second longest running professional football league in the United States after the NFL, although its current incarnation is a separate entity from the original, which folded due to bankruptcy in 2008. From its debut until 1997, the Arena Football League operated with a monopoly on the indoor game, due to a broad interpretation that virtually all of the league's rules, collectively known as arena football, were covered under its patent; the Professional Indoor Football League successfully defeated the AFL's legal action against it in 1997, opening the possibility for other indoor football leagues to form. Only one significant aspect of the patent, the large rebound nets the AFL has used since its debut to keep balls in play, was fully protected; the patent expired in 2007, although no other professional indoor league has adopted rebound nets since. As of 2011, two national leagues (the AFL and the Indoor Football League), along with several regional professional and semi-pro leagues, are in operation. As of 2011, no professional indoor football league has had any significant presence in Canada (despite an abundance of hockey arenas that are ideal for the game); only one indoor team, the AFL's short-lived Toronto Phantoms (2000 to 2002), has ever played its games in Canada. The all-female Lingerie Football League had operations in Canada from 2011 to 2014, but that league dropped to amateur level by the time the LFL entered the country.