The American Association (AA) was a Major League Baseball league that existed for 10 seasons from 1882 to 1891. During that time, it challenged the National League (NL) for dominance of professional baseball. Together with the NL, the AA participated in an early version of the World Series seven times.

The American Association distinguished itself in several ways from what it considered to be the puritanical National League. The new league established teams in what the NL leaders pejoratively called "river cities", including Pittsburgh, Cincinnati, Louisville and St. Louis, with the inherent implication of lower morality or social standards in those cities.

Living "down" to those expectations, the AA offered cheaper ticket prices and more liberal libations to its patrons. On November 8, 1881, at the Gibson House in Cincinnati, it was decided that individual teams in the newly formed league would operate its own affairs and setting its own admission prices, under an agreement called the guarantee system. The NL at that time prohibited the sale of alcohol on its grounds, while the AA had no such restrictions, especially as several of its teams were backed by breweries and distilleries. The AA became known as "The Beer and Whiskey League", another pejorative term applied by NL supporters, and which did not seem to bother the fans of the Association's clubs.

Beginning in 1884 and continuing through 1890, the champion of the AA met the champion of the National League in an early version of the World Series. These early Series were less organized than the modern version, with as few as three games played and as many as fifteen, and the contests of 1885 and 1890 ending in disputed ties. The NL won four of these Series, while the AA won only one, in 1886 when the St. Louis Browns (now Cardinals) defeated the Chicago White Stockings (now Cubs).

Over its lifetime, the AA was weakened by several factors. One was the tendency of some of its teams to jump to the NL. The consistently stronger NL was in better position to survive adverse conditions. The most significant blow to the AA was dealt by the Players' League, a third major league formed in 1890, which siphoned off talent and gate receipts. In a unique historical oddity, the Brooklyn Bridegrooms (now the Los Angeles Dodgers) won the league's championship and represented the AA in the 1889 World's Series, switched to the NL during the off-season, and then repeated the same feat.

The living legacy of the old Association is the group of teams that came over to the National League to stay. The Pirates moved to the NL after the 1886 season, the Bridegrooms/Dodgers and the Cincinnati Reds after the 1889 season, and the Browns/Cardinals after the American Association folded following the 1891 season. Following the reorganization and contraction of the NL from 12 teams down to 8 in 1900, half of the eight surviving teams were former members of the AA. Several of the AA's home-field venues survived into the 1960s: The ballpark used by the 1891 Washington club, evolved into Griffith Stadium; the home of the St. Louis Browns, Sportsman's Park; and the city block occupied by the Reds, which evolved into Crosley Field. Crosley was the last physical remnant of the AA to go, other than the clubs themselves, when it was replaced by a new stadium in mid-1970.

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