|Founded||January 28, 1901|
|President||Jackie Autry (honorary)|
|No. of teams||15|
|Most recent champion(s)||Detroit Tigers (11th)|
|Most titles||New York Yankees (40)|
The American League of Professional Baseball Clubs, or simply the American League (AL), is one of two leagues that make up Major League Baseball in the United States and Canada. It developed from the Western League, a minor league based in the Great Lakes states, which eventually aspired to major league status. It is often called the Junior Circuit because it claimed Major League status for the 1901 season, 25 years after the formation of the National League (the "Senior Circuit").
At the end of every season, the American League champion plays in the World Series against the National League champion. Through 2012, American League teams have won 62 of the 108 World Series played since 1903, with 27 of those coming from the New York Yankees alone. The 2012 American League champions are the Detroit Tigers. The New York Yankees have won 40 American League titles, the most in the league's history, followed by the Philadelphia/Kansas City/Oakland Athletics (15) and the Boston Red Sox (12).
Originally a minor league known as the Western League, the league later developed into a major league after the American Association disbanded. In its early history, the Western League struggled until 1894, when Ban Johnson became the president of the league. Johnson led the Western League into major league status and soon became the president of the newly renamed American League. Babe Ruth, noted as one of the most prolific hitters in Major League Baseball history, spent the majority of his career in the American League. The American League has one notable difference over the National League, in that since 1973 it has had the designated hitter rule. Under the rule, a team may use a batter in its lineup who is not in the field defensively, usually replacing the pitcher in the batting order, compared to the old rule that made it mandatory for the pitcher to hit.
In 1977, the league expanded to fourteen teams, when the Seattle Mariners and Toronto Blue Jays were enfranchised. Granting a team to Toronto marked the AL's expansion to Canada, following the National League's expansion to Montreal, and the Mariners were added in an attempt to settle a pending $90 million lawsuit against the league by the city of Seattle over the quick departure of the Seattle Pilots in 1970.
Until the late 1970s, league umpires working behind home plate wore large, balloon-style chest protectors worn outside the shirt or coat, while their brethren in the National League wore chest protectors inside the shirt or coat. In 1977, new umpires (including Steve Palermo) had to wear the inside chest protector, although those on staff wearing the outside protector could continue to do so. Most umpires made the switch to the inside protector, led by Don Denkinger in 1975 and Jim Evans the next year, although several did not, including Bill Haller, Lou DiMuro, George Maloney and Jerry Neudecker, who became the last Major League umpire to use the outside protector in 1985.
In 1994, the league, along with the National League, reorganized again, into three divisions (East, West, and Central) and added a third round to the playoffs in the form of the League Divisional Series, with the best second-place team advancing to the playoffs as a wild-card team, in addition to the three divisional champions. In 1998, the newly franchised Tampa Bay Devil Rays joined the league, and the Arizona Diamondbacks joined the National League: i.e., each league each added a fifteenth team. An odd number of teams per league meant that at least one team in each league would have to be idle on any given day, or alternatively that odd team out would have had to play an interleague game against its counterpart in the other league. The initial plan was to have 3 five-team divisions per league with interleague play year-round—possibly as many as 30 interleague games per team each year. For various reasons, it soon seemed more practical to have an even number of teams in both leagues. So, the Milwaukee Brewers agreed to change leagues, moving from the AL Central to the NL Central. At the same time, the Detroit Tigers shifted over to the AL Central, making room for the Devil Rays in the East. Following the move of the Houston Astros to the American League in 2013, both leagues now consist of 15 teams.
For the first 96 years, American League teams faced their National League counterparts only in exhibition games or in the World Series. Beginning in 1997, interleague games have been played during the regular season and count in the standings. As part of the agreement instituting interleague play, the designated-hitter rule is used only in games where the American League team is the home team. Through the 2012 season, the Yankees have won the most American League pennants (40), followed by the Athletics (15), Red Sox (12), and Tigers (11). Likewise, the Yankees have also won the most World Series (27), with the Athletics second in the American League with nine, the Red Sox third with seven, and the Tigers fourth with four.
Charter franchises 
There were eight charter teams in 1901, the league's first year as a major league, and the next year the original Milwaukee Brewers moved to St. Louis to become the St. Louis Browns. These franchises constituted the league for 52 seasons, until the Browns moved to Baltimore and took up the name Baltimore Orioles. All eight original franchises remain in the American League, although only four remain in the original cities (Detroit, Chicago, Boston, and Cleveland). The eight original teams and their counterparts in the "Classic Eight" were:
- Baltimore Orioles (became the New York Highlanders in 1903 changed to New York Yankees in 1913)
- Boston Americans (became the Boston Red Sox in 1908)
- Chicago White Stockings (became the Chicago White Sox in 1903)
- Cleveland Bluebirds (became the Cleveland Indians in 1915)
- Detroit Tigers (name and locale unchanged from 1894 forward)
- Milwaukee Brewers (became the St. Louis Browns in 1902 and the Baltimore Orioles in 1954)
- Philadelphia Athletics (became the Kansas City Athletics in 1955 and the Oakland Athletics in 1968)
- Washington Senators (became the Minnesota Twins in 1961)
Expansion, renaming, and relocation summary 
- 1902: Milwaukee Brewers move to St. Louis, renamed St. Louis Browns
- 1902: Cleveland Blues renamed Cleveland Bronchos
- 1903: Baltimore Orioles move to New York, renamed New York Highlanders (informal nickname)
- 1903: Chicago White Stockings officially renamed Chicago White Sox
- 1903: Cleveland Bronchos renamed Cleveland Naps
- 1905: Washington Senators renamed Washington Nationals; Senators name continued to be used by media
- 1908: Boston Americans (informal nickname) formally named Boston Red Sox
- 1913: New York Highlanders nickname dropped in favor of already-established alternative, New York Yankees
- 1915: Cleveland Naps renamed Cleveland Indians
- 1954: St. Louis Browns move to Baltimore, renamed Baltimore Orioles
- 1955: Philadelphia Athletics move to Kansas City
- 1957: Washington Nationals/Senators formally renamed Washington Senators
- 1961: Washington Senators move to Minneapolis-St. Paul, renamed Minnesota Twins
- 1961: Los Angeles Angels and new Washington Senators enfranchised
- 1965: Los Angeles Angels renamed California Angels in mid-season on September 2, 1965. For the following season, the Angels moved within the Los Angeles metropolitan area from the city of Los Angeles to the Orange County suburb of Anaheim.
- 1968: Kansas City Athletics move to Oakland
- 1969: Kansas City Royals and Seattle Pilots enfranchised
- 1970: Seattle Pilots move to Milwaukee, renamed Milwaukee Brewers. (Four years earlier, in 1966, the National League's Milwaukee Braves had moved to Atlanta.)
- 1972: Washington Senators move to Dallas-Ft. Worth (Arlington), renamed Texas Rangers
- 1973: Oakland Athletics officially renamed Oakland A's
- 1977: Seattle Mariners and Toronto Blue Jays enfranchised
- 1980: Oakland A's officially renamed Oakland Athletics
- 1997: California Angels renamed Anaheim Angels. The change came more than 30 years after the team's move to Anaheim.
- 1998: Tampa Bay Devil Rays, representing Tampa-St. Petersburg, enfranchised
- 1998: Milwaukee Brewers transfer from the American League to the National League. (See above.)
- 2005: Anaheim Angels renamed Los Angeles Angels of Anaheim
- 2008: Tampa Bay Devil Rays renamed Tampa Bay Rays
- 2013: Houston Astros transfer from the National League Central to the American League West.
Current teams 
American League East 
- Baltimore Orioles enfranchised 1901 as the Milwaukee Brewers, moved to St. Louis (1902) and to Baltimore (1954)
- Boston Red Sox enfranchised 1901 as the Americans (changed name to Red Sox in 1908)
- New York Yankees enfranchised 1901* as the Baltimore Orioles, moved to New York (1903)
- Tampa Bay Rays enfranchised 1998 as the Tampa Bay Devil Rays (team name changed in 2008)
- Toronto Blue Jays enfranchised 1977
American League Central 
- Chicago White Sox enfranchised 1894 as the Sioux City Cornhuskers, moved to St. Paul (1895) and to Chicago (1900)
- Cleveland Indians enfranchised 1894 as the Grand Rapids Rustlers, moved to Cleveland (1900)
- Detroit Tigers enfranchised 1894
- Kansas City Royals enfranchised 1969
- Minnesota Twins enfranchised 1894 as the Kansas City Blues, moved to Washington (1901), and to Minneapolis-St. Paul (1961)
American League West 
- Houston Astros enfranchised 1962 in National League as the Houston Colt .45s (team changed name in 1965), transferred to American League (2013)
- Los Angeles Angels of Anaheim enfranchised 1961 as the Los Angeles Angels, moved within the Los Angeles area to Anaheim (1966)
- Oakland Athletics enfranchised 1901* in Philadelphia, moved to Kansas City (1955) and to Oakland (1968)
- Seattle Mariners enfranchised 1977
- Texas Rangers enfranchised 1961 as the Washington Senators, moved to Arlington (1972)
(*)See commentary on Western League page. The Indianapolis and Minneapolis teams were replaced by teams in Baltimore and Philadelphia in 1901, but it is unclear and disputed as to which team went where.
American League presidents, 1901–1999 
Other leagues 
Several other sports have had leagues called "American League," usually with the sport name as a qualifier, such as the "American Football League" (which eventually merged with the National Football League, adopting the latter's name for the combination). The American Hockey League is the top minor league in North American professional ice hockey.
See also 
- List of American League pennant winners
- American League Championship Series (ALCS)
- American League Division Series (ALDS)
- List of American League Wild Card winners
- Major League Baseball
- National League
- World Series
- The National League Story, Lee Allen, Putnam, 1961.
- The American League Story, Lee Allen, Putnam, 1962.
- The Baseball Encyclopedia, published by MacMillan, 1968 and later.
- For more details, see Milwaukee Brewers#1994–98: Realignment / "We're taking this thing National"