Major professional sports leagues in the United States and Canada

Relations between leagues[edit]

Although they are competitors, at times the "Big Four" leagues also cooperate. Some owners have teams in multiple leagues. In the early years of professional basketball, the American Basketball League, the de facto major league of the 1920s, was backed primarily by NFL owners. There are common business and legal interests; the leagues will often support one another in legal matters since the courts' decisions might establish precedents that affect them all. One recent example was the US Supreme Court decision in 2010 in American Needle, Inc. v. National Football League, in which the NFL (which ultimately lost the case) received amicus curiae briefs from the NBA, NHL, and MLS.^[145] The leagues' commissioners occasionally meet in person, most recently in 2009.^[146]


The leagues also cooperate in the construction and use of facilities. Many NBA and NHL teams share arenas, and, in years past, such sharing was very common for MLB and NFL teams. Multi-purpose stadiums were built to accommodate multiple sports in the later half of the 20th century; the last multi-purpose stadium in the NFL, what is now Rickey Henderson Field at RingCentral Coliseum, hosted its last NFL game in 2019. Even in situations where separate stadiums have been constructed for each team (as is generally the norm in the 21st century), the individual stadiums may be constructed adjacent to each other and share parking space and other infrastructure. More recently, MLS teams have used NFL and CFL stadiums as either full-time home fields (much less so now, due to the league's insistence on soccer-specific stadiums) or for special event games; in reverse, in at least one case, an NFL team (the Los Angeles Chargers) used a soccer-specific MLS stadium on a temporary basis from 2017 to 2019 while a larger stadium was built for them. In recent years, two MLS teams have shared stadiums permanently with NFL teams that were explicitly built to host both sports. Seattle Sounders FC share Lumen Field with the Seattle Seahawks; the Seahawks were owned by Paul Allen, also a member of the Sounders ownership group, until his death in 2018. Atlanta United FC shares Mercedes-Benz Stadium with the Atlanta Falcons, with both teams under the ownership of Arthur Blank. Charlotte FC shares Bank of America Stadium with the Carolina Panthers; both teams are owned by David Tepper. In Canada, Vancouver Whitecaps FC share BC Place with the CFL's BC Lions. The Seattle, Atlanta, and Vancouver stadiums are designed to have reduced seating capacity for most MLS games. Charlotte's stadium was renovated to allow for lower capacity soccer crowds before the MLS team debuted in 2022. Additionally, the New England Revolution shares Gillette Stadium with the New England Patriots, New York City FC shares Yankee Stadium with the New York Yankees MLB team, which also owns part of NYCFC, and Toronto FC shares BMO Field with the CFL's Toronto Argonauts, with both teams now owned by Maple Leaf Sports & Entertainment, the company that also owns the Toronto Raptors and the Toronto Maple Leafs.


Also notable in recent years have been the NHL's Winter Classic and Heritage Classic, which have been held in NFL, CFL, and MLB, as well as college football, stadiums. A unique situation is the TD Place Complex in Ottawa; the same structure serves as the indoor Ottawa Civic Centre (which hosted the NHL's Senators in the 1990s), while on the roof of that arena was seating for Frank Clair Stadium (at that time home of the CFL's Ottawa Rough Riders; by 2014 the stadium was renovated into TD Place Stadium and is now home to the CFL's Ottawa Redblacks).


In the early years of the NFL and to a lesser extent the NHL, it was not uncommon for teams to share nicknames with their MLB counterparts. For example, until 1957 New York City played host to baseball and football Giants. MLB's Pittsburgh Pirates shared its nickname with an NFL team (which ultimately became the Pittsburgh Steelers) as well as a now-defunct early NHL team, while the Canadian football team Hamilton Tigers shared a team name with an NHL team. The most recent example of two major teams sharing a franchise name was between 1960 and 1987; when the NFL's Chicago Cardinals relocated to St. Louis, Missouri, it was allowed to keep the Cardinals name despite the established existence of a baseball team of the same name.


In 1997, the NFL loaned $3 million to the CFL after the latter's failed expansion into the United States market in the early 1990s left it in financial danger.^[147]


In 2015, the NHL partnered with MLB's digital arm Major League Baseball Advanced Media (MLBAM) to assume the operations of its digital properties; the league's television network NHL Network was also taken over by the staff of MLB Network and re-located to its facilities.^{[148][149][150]}


The NBA Finals of the NBA and the Stanley Cup Finals of the NHL are the championship series of their respective leagues, which occur in June.