The American League of Professional Baseball Clubs, or simply the American League (AL), is one of two leagues that make up Major League Baseball (MLB) 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 sometimes 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; two seasons did not end in playing a World Series. Through 2015, American League teams have won 64 of the 111 World Series played since 1903, with 27 of those coming from the New York Yankees alone. The 2014 and 2015 American League champions are the Kansas City Royals. 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 (13).
(詳細はminor league known as the Western League, the American 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, replacing any player (usually the pitcher) in the batting order, compared to the old rule that made it mandatory for the pitcher to bat.〔(【引用サイトリンク】url=http://www.americanwestbl.com/league-history/ )〕
In 1969, the league reorganized into two divisions (American League East and American League West), as did the National League, and added another round to the playoffs in the form of the American League Championship Series, with the first place team in each division advancing to the playoffs.
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 MLB 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 American League Division 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 three five-team divisions per league with inter league 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. The Milwaukee Brewers agreed to change leagues, moving from the AL Central to the NL Central. At the same time, the Detroit Tigers were moved from the AL East 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 2015 season, the Yankees have won the most American League pennants (40), followed by the Athletics (15), Red Sox (13), 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 eight, and the Tigers fourth with four.
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