MLB (Major League Baseball) is a professional baseball league, consisting of teams that play in the National League and the American League. After 100 years as separate legal entities,

the two leagues merged in 2000 into a single organization led by the Commissioner of Baseball.

MLB constitutes one of the major professional sports leagues of Canada and the United States. It is composed of 30 teams —one in Canada and 29 in the United States. With the International Baseball Federation, MLB (Major League Baseball) also manages the World Baseball Classic. It has the highest season attendance of any sports league in 2011.