The American League of Professional Baseball Clubs, the second of the two leagues making up Major League Baseball played their first season in 1901, twenty-five years after the rival National League began. Their roots can be traced back to the Western League of the 1890s who's "clean cut" image helped propell popularity eventually being promoted to major league status.
The inaugural season saw the league made up of eight franchises: Baltimore Orioles, Boston Somersets, Chicago White Stockings, Cleveland Blues, Detroit Tigers, Milwaukee Brewers, Philadelphia Athletics, and Washington Senators. Battles with the NL for top talent was agressive in early seasons, the AL's lack of salary caps helped lure the best away from the NL. A peace agreement was reached between the two following 1902 leading to the creation of the World Series, a championship series between the winners of the two leagues beginning in 1903 still held to this day.
After Baltimore relocated to New York in 1903 the league remained stable until 1954 when Baltimore re-joined the league courtesy St. Louis moving east. Expansion took place for the first time in 1961 with further expansions in 1969, 1977, and 1998. Franchise swapping has happened twice with Milwaukee going from the AL to NL in 1998 and Houston going the opposite way 15 years later in 2013. As of the end of 2011 the New York Yankees have won the most AL championships winning 40 times, the Philadelphia/Oakland Athletics franchise is second with 14.