When it was founded in 1925, the league included six teams (74 Regimiento, México, Agrario, Nacional, Guanajuato and Águila). Since then, the league has expanded to sixteen teams, divided equally into a north and a south zone, the champions of which meet to contest a best-of-seven gameplayoff series. The season begins in mid-March with the playoffs running through mid-August.
1949: Landmark ruling of Gardella v. Chandler
Judges use Federal Baseball Club of Baltimore v. National League of Professional Baseball Clubs to uphold that the baseball leagues and commissioner are not violating anti-trust rulings because they are not doing anything different from what was done when the previous ruling occurred. Included in the previous ruling was the fact that the baseball leagues could transmit information about their games via telegraph wires. And, because the leagues are only negotiating, their actions in negotiating the television and radio broadcasts are no different from their actions with telegraphs. Therefore the previous decision can be upheld. Judges also assert that this the previous decision hasn't been objected by Congress, so it must also be of the opinion of congress that baseball does not fall under the rules of the Anti-Trust Act. (Of course, consider that some judges felt differently, but ruling was overall in favor of the Leagues.)
The ruling went untested until the Mexican League was formed. Players who went to play in the Mexican League got blacklisted from MLB. One such player, Danny Gardella, was blacklisted because he had broken his contract and gone to play professional baseball in Mexico.
In 1948, Gardella brought a claim against Commissioner of Baseball Happy Chandler, the National League and American League, as well as their presidents (Ford Frick and Will Harridge, respectively). Gardella charged that they were engaged in interstate commerce because the defendants had made contracts with radio broadcasting and television companies that sent narratives or moving pictures of the games across state lines. MLB then settled with Gardella and offered all Mexican League jumpers amnesty—protected the ambiguity surrounding the antitrust protection.
In 1949, baseball player Danny Gardella won a landmark appeal to baseball's reserve clause in the federal courts. This successful appeal is recognized as the first major step towards baseball free agency.
In 1979, the Mexican Central League was absorbed into the expanded Liga Mexicana de Beisbol (Mexican Baseball League). The newly expanded league now featured a 20-team circuit with four divisions. However, after a series of team bankruptcies, the Mexican League was reduced to 14 teams in two divisions.