MLB
Major League Baseball (MLB) is a North American professional baseball league consisting of teams that play in the American League and National League. The two leagues, dating to 1901 and 1876 respectively as separate legal entities, merged in 2000 into a single organization led by the Commissioner of Baseball.

MLB constitutes one of the four major professional sports leagues of the United States and Canada. It is composed of thirty teams: twenty-nine in the United States and one in Canada. Teams in MLB play 162 games each season over six months (April through September). Five teams in each league advance to a four-round postseason tournament that culminates in the World Series, a best-of-seven-games championship series between the two league champions that dates to 1903.

The organization oversees many minor-league baseball leagues, which operate about 240 teams affiliated with the major-league clubs. With the International Baseball Federation, the league also manages the international World Baseball Classic tournament. MLB has the highest season attendance of any sports league in the world with nearly 75 million spectators in 2012.