In North America, the term Major League Baseball generally refers to the top-level caliber of baseball play. Leagues in other parts of the world, notably Japan and Latin America, may have equivalent levels of play (and increasingly draw from the same talent pools), but are typically not included when the term is used.

More specifically, "Major League Baseball" (MLB) refers to the two top leagues, the National League and the American League, and the joint organizational structure which has existed between them since 1901. MLB has a Commissioner, maintains joint umpiring crews, and negotiates marketing and television contracts for the two major leagues. This structure and the major league ownership of minor league baseball is possible because of a 1922 court decision in which baseball was ruled a local affair and not interstate commerce subject to antitrust law, an exemption which does not apply to other sports.

Table of contents
1 Current Major Leagues
2 Historical Major Leagues
3 Related articles
4 External links

Current Major Leagues

The Major League Baseball season runs from early April through late September. Players and teams prepare for the season in February and March in spring training. There are 30 teams in the two leagues, 14 in the American League (AL) and 16 in the National League (NL), and each league is split into three divisions: East, Central, and West. Games are mostly played against teams within the same league, and those are usually weighted towards teams in the same division. Games were played exclusively within each league (excepting the World Series) until interleague play was introduced in 1997. Thus, teams like the New York Yankees in the AL and the New York Mets in the NL now play each other every year, instead of only possibly meeting in the World Series.

The season is 162 games long. Until 1961, the season was 154 games long. In early July, around the midpoint in the season, there is a three day "All-Star break" during which the Major League Baseball All-Star Game takes place, an exhibition game featuring the best players from each league playing one another.

In October, at the end of the regular season, the postseason begins for the eight teams that make the playoffs. Until 1969, when there were no divisions, the team finishing with the best record in each league won the league's pennant and faced the other league's pennant winner in the fall classic, the World Series. When the league expanded in 1969, each league split into Eastern and Western divisions. To determine the pennant winner, the two division leaders squared off in the American League Championship Series (ALCS) and National League Championship Series (NLCS).

After subsequent expansions, the leagues realigned again in 1994 into the current East, Central, West makeup. The three division leaders plus a "Wild Card" team now face off in the playoffs. The Wild Card team is the team with the best record in the league that did not win a division. The four teams face off in the Division Series to determine which teams head to the League Championship Series for a chance at the league's pennant. The Wild Card winner faces the division winner with the best record, unless the teams are in the same division, in which case the Wild Card team plays the second-best division winner. (See American League Division Series and National League Division Series.)

The National League champion and American League champion battle each other in the October season finale, the World Series.

At the time of writing the Commissioner of Baseball, Bud Selig, has often floated the idea of further expansion and realignment of the major leagues. At the moment, however, the major leagues are each split into three divisions, and structured as follows:

American League

WestCentralEast
Anaheim Angels Chicago White Sox Baltimore Orioles
Oakland Athletics Cleveland Indians Boston Red Sox
Seattle Mariners Detroit Tigers New York Yankees
Texas Rangers Kansas City Royals Tampa Bay Devil Rays
  Minnesota Twins Toronto Blue Jays

National League

WestCentralEast
Arizona Diamondbacks Chicago Cubs Atlanta Braves
Colorado Rockies Cincinnati Reds Florida Marlins
Los Angeles Dodgers Houston Astros Montreal Expos
San Diego Padres Milwaukee Brewers New York Mets
San Francisco Giants Pittsburgh Pirates Philadelphia Phillies
 St. Louis Cardinals 

Historical Major Leagues

In 1969, the centennial of professional baseball, a commission chartered by Major League Baseball identified the following leagues as "major leagues". The list is sometimes disputed by baseball researchers. The MLB list included the following:

Some researchers contend that the National Association (1871-1875), the Negro Leagues (primarily during the years from 1921-1946), and the first year of the American League (1900) deserve consideration as major leagues due to the caliber of player and the level of play exhibited. However, game and statistical records for these particular leagues were not kept in a consistent manner.

Related articles

Players and officials

Statistics and records

Post-season awards

Exhibition and playoffs

External links