Major League Baseball (MLB) is an American professional baseball organization and the oldest of the major professional sports leagues in the United States and Canada. A total of 30 teams play in Major League Baseball: 15 teams in the National League (NL) and 15 in the American League (AL). The NL and AL were formed as separate legal entities in 1876 and 1901, respectively. Beginning in 1903, the two leagues cooperated but remained legally separate entities. In 2000 the leagues merged into a single organization led by the Commissioner of Baseball.