The following is a timeline of franchise evolution in Major League Baseball. The histories of franchises in the National Association of Base Ball Players (NABBP), National Association of Professional Base Ball Players (NA), Union Association (UA), and American Association (AA) before they joined the National League (NL) are also included. In 1900 the minor league Western League renamed itself the American League (AL). All of the 1899 Western League teams were a part of the transformation with the Saint Paul Apostles moving to Chicago and to play as the White Stockings. In 1901 the AL declared itself a major league. For its inaugural major league season the AL dropped its teams in Indianapolis, Buffalo and Minneapolis and replaced them with franchises in Boston, Philadelphia, and Baltimore and the Kansas City Blues moved to Washington to play as the Senators.
The timeline has not yet been fully updated to reflect that designation (in addition, the timeline does not include any non-National League/American League teams which existed at the major league level from 1876 to 1915).
The History of organizational changes section includes all leagues which have been designated as major league by MLB, listed chronologically by founding date:
The first line is the formation of the National League in 1876, and the second is the transformation of the American League to a major league in 1901. The third line is the beginning of the expansion era in 1961. The fourth line marks the legal merger of the American and National Leagues into a single Major League Baseball.
World Series championships are shown with a "*", National League Pennants before the World Series are shown with a "^", and American League Pennants before the World Series are shown with a "#". No World Series was played in 1904, so the pennant winners for each league are indicated. Due to the 1994–95 Major League Baseball strike, there were no pennant or World Series winners in 1994, so this year is left blank.
Note: Team names are given here according to the convention used by The Baseball Encyclopedia, which regularized them into the familiar form of modern team names. However, most teams in the early period had no name, aside from that of the club (as in "Hartford Base Ball Club" or "Athletic Base Ball Club of Philadelphia"), and nicknames like "Beaneaters," "Perfectos" and the many allusions to uniform colors were inventions by the florid sportswriters of the day.[2]
The Cincinnati Red Stockings transferred to the NL and became the Cincinnati Reds.
The Indianapolis Hoosiers, Kansas City Cowboys, and Washington Nationals folded.
The Baltimore Orioles transferred to Minor League Baseball and were replaced by the Brooklyn Gladiators. The Brooklyn Gladiators then folded mid-season, and the Baltimore Orioles returned to the AA to finish the season.
Following the fallout from the 1919 Black Sox Scandal, in November 1920, the National Baseball Commission was replaced by the Commissioner of Baseball, who acts as the chief executive officer of major and minor leagues.[3][4]
The Dayton Marcos departed the NNL as an independent team.
The Cleveland Tate Stars departed from the NNL as an independent team and were replaced by the Toledo Tigers. The Toledo Tigers then folded mid-season, and the Cleveland Tate Stars returned to the NNL as an associate member to finish the season.
Only season in NNL §
Only season in NNL, folded mid-season §§
Associate member, joined mid-season, team folded after season ^
1923 major league teams & 1923 major Negro league teams
The Columbus Blue Birds joined the NNL. The team disbanded and merged with the independent Akron Black Tyrites after the first half of the split season. The Akron Black Tyrites joined the NNL in place of the Columbus Blue Birds as the Akron Grays before they moved to Cleveland, Ohio and became the Cleveland Giants for one game.
First season in NNL *
Team moved from former EWL or NSL **
Only season in NNL, folded mid-season §
Only season in NNL, joined mid-season §§
Team folded after this season ^
Team departed after this season ^^
1933 major league teams & 1933 major Negro league teams
The St. Louis–New Orleans Stars reformed and joined the NNL as the Harrisburg–St. Louis Stars, since they moved to Harrisburg, Pennsylvania; although, they kept the St. Louis moniker as a part of their name. The team proceeded to withdraw in July to barnstorm, and then they folded.
MLB realigned to three divisions in each league to accommodate an expanded postseason format with a wild card team (although this new playoff format would not be fully implemented until 1995 due to a work stoppage):
The AL Central was formed with the Cleveland Indians and Milwaukee Brewers transferring from the AL East, and the Chicago White Sox, Kansas City Royals, and Minnesota Twins transferring from the AL West.
The NL Central was formed with the Chicago Cubs, Pittsburgh Pirates, and St. Louis Cardinals transferring from the NL East, and the Cincinnati Reds and Houston Astros transferring from the NL West.
In order to primarily continue interleague play, the Milwaukee Brewers transferred to the NL Central so both leagues would have an even number of teams.
With interleague play expanded to occur throughout the season, the Houston Astros transferred to the AL West to accommodate each league with 15 clubs apiece.
^According to the National League's 1877 Constitution, the member clubs were given as "Boston B. B. Club, Chicago B. B. Club, Cincinnati B. B. Club, Hartford B. B. Club, Louisville B. B. Club, St. Louis B. B. Club." Constitution and Playing Rules of the National League of Professional Base Ball Clubs. Chicago, A. G. Spalding 1877.
