Four major professional sports

The major professional sports leagues in the United States and Canada are the highest professional competitions of team sports in the United States and Canada. The four leagues universally included in the definition are Major League Baseball (MLB), the National Basketball Association (NBA), the National Football League (NFL), and the National Hockey League (NHL). Other prominent leagues include Major League Soccer (MLS) and the Canadian Football League (CFL).

The MLB, NBA, NFL and NHL are commonly referred to as the "Big 4". Each of these is the wealthiest professional club competition in its sport worldwide, and along with the English Premier League they make up the top five sports leagues by revenue in the world. In addition, the sports of these four leagues were all developed in their modern forms in North America, and all except American football have become popular internationally. Because the leagues enjoy a significant place in popular culture in the U.S. and Canada, the best players from these leagues often become cultural icons in both countries.

Currently, the NFL has 32 teams, and the others have 30 each (with the NHL expanding to 31 teams in 2017). The vast majority of major league teams are concentrated in the most populous metropolitan areas of the United States and Canada. Unlike the promotion and relegation systems used in sports leagues in various other regions around the world, those teams in the North American sports leagues remain static from season-to-season, unless they are disbanded or relocated. Each Big Four league, as well as Major League Soccer and the Canadian Football League, averages at least 15,000 fans in attendance per game as of 2015.

Baseball, football, and hockey have had professional leagues continuously for over 100 years; early leagues such as the National Association, Ohio League, and National Hockey Association formed the basis of the modern MLB, NFL, and NHL, respectively. Basketball was invented in 1891 and its first professional league formed in the 1920s. The Basketball Association of America formed the basis of the NBA. Soccer was first professionalized in 1894, but leagues suffered greatly from lack of sustainability and seldom lasted more than a decade. Soccer's greatest successes were in the form of the American Soccer League (1921–1933), the original North American Soccer League (1968–84), and, currently, Major League Soccer (1996–present).

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