The 1887 major league baseball season began on April 16, 1887. The regular season ended on October 10, with the Detroit Wolverines and the St. Louis Browns as regular season champions of the National League and American Association, respectively. The postseason began with Game 1 of the fourth World's Championship Series on October 10 and ended with Game 15 on October 26, in what was a best-of-fifteen-playoff, played across 10 cities. The Wolverines defeated the Browns, ten games to five (and clinching on Game 11), capturing their first World's Championship Series.
The Louisville Colonels set a Major League record which still stands for the most base on balls for a team in a game, with 19 against the Cleveland Blues on 21 September.
Over the offseason, the National League's Kansas City Cowboys folded, and saw them replaced by the American Association's Pittsburgh Alleghenys. In place of the Alleghenys leaving the AA for the NL, the Cleveland Blues were enfranchised. Meanwhile, the St. Louis Maroons relocated to Indianapolis, Indiana as the Indianapolis Hoosiers.
On July 14, Chicago was to play an exhibition game against the Eastern League Newark team, who were set to play black players Moses Fleetwood Walker (who formerly played in the majors in three years prior) and George Stovey (who the New York Giants had their eyes on signing). With threats from Chicago to not play against Newark if Walker and Stovey played, they were substituted for the game. Between Chicago's financial threats to not play against teams with people of color and other minor league teams creating petitions to force teams to release players of color, Organized Baseball effectively set up the baseball color line.
The color line would remain firm for 60 years until the Brooklyn Dodgers called up Jackie Robinson in , breaking the color line. The process of integration would then last for another 12 years until , when the last major league team, the Boston Red Sox integrated by calling up Pumpsie Green.
The 1887 schedule consisted of 140 games for all American Association teams and 126 games for all National League, each of which had eight teams. Each AA team was scheduled to play 20 games against the other seven teams, while each NL team was scheduled to play 18 games against the other seven teams. Both the AA's 140-game format and NL's 126-game format were continued from their implementation the previous season. The NL would adopt the AA's format the following season, and each league would use this 140-game format until .
American Association Opening Day took place on April 16 featuring all eight teams, while National League Opening Day took place on April 27, featuring four teams. The American Association would see its final day of the regular season on October 10 with four teams, while the National League would see its final day of the season on October 8, featuring all eight teams. The 1887 World's Championship Series took place between October 10 and October 26.
The 1887 season saw many radical changes which affected the game, as well as unity on rules by the American Association and National League. The following rule changes were made:
Two teams played in two neutral site games in which they were treated as the home team. Meanwhile, blue laws restricted Sunday activities in several localities, causing several teams of the American Association (which was informally referred to as the "Beer & Whiskey League" due to its openness on alcohol, compared to the National League) to play at ballparks in a different locality.
30 tie games (14 in AA, 16 in NL), which are not factored into winning percentage or games behind (and were often replayed again), occurred throughout the season.
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In 1887, bases on balls (walks) were counted as hits by the major leagues in existence at the time. This inflated batting averages, with 11 players batting .400 or better, and the experiment was abandoned the following season. Historical statistics for the season were later revised, such that "Bases on balls shall always be treated as neither a time at bat nor a hit for the batter." This results in ambiguity for some players' season and career hits totals, notably with Cap Anson. Anson was credited with a .421 average and the National League batting title in 1887; however, the recalculation of averages with walks excluded lowered his average to .347 and retroactively gave the batting title to Sam Thompson. The 1887 batting average and hits are included below, using contemporary data on Baseball Reference.
<sup>1</sup> American Association Triple Crown batting winner<br> <sup>2</sup> All-time single-season stolen bases record
The Cleveland Blues join the American Association and play at National League Park in Cleveland, Ohio.
The 1887 season saw two teams relocate to new ballparks:
The first structure of the South End Grounds, home of the Boston Beaneaters, would see its last game on September 10, seeing a completely new structure built over the following offseason.
For various reasons, two teams would play home games at neutral sites:
Three teams of the American Association hosted Sunday games: