Professional baseball

Professional baseball is played in leagues throughout the world. In these leagues, and associated farm teams, baseball players are selected for their talents and are paid to play for a specific team or club system.

Major League Baseball in the United States and Toronto, Canada, consists of the National League (founded in 1876) and the American League (1901). Historically, teams in one league never played teams in the other until the World Series, in which the champions of the two leagues played against each other. This changed in 1997 with the advent of interleague play.

In addition to the major leagues, many North American cities and towns feature minor league teams. An organization officially styled Minor League Baseball, formerly the National Association of Professional Baseball Leagues, oversees nearly all minor league baseball in the United States and Canada. The minor leagues are divided into classes AAA, AA, High A, Low A, Short-Season A, Advanced Rookie, and Rookie. These minor-league divisions are affiliated with major league teams, and serve to develop young players and rehabilitate injured major-leaguers. The Mexican League is a Minor League Baseball member league that operates without affiliations to Major League teams. The phrase "Organized Baseball" is often applied as an umbrella term for all leagues — Major and minor — under the authority of the Commissioner of Baseball.

Operating outside the Minor League Baseball organization are many independent minor leagues such as the Atlantic League, American Association, Frontier League, Can-Am League.

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