# Timeline of Major League Baseball

The following is a timeline of franchise evolution in Major League Baseball.

## Background

    Source: The Baseball Encyclopedia (10 ed.). Macmillan General Reference. 1996. ISBN 978-0028608150.
    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.
The National Association of Base Ball Players (NABBP) was the first organization to govern baseball. The succeeding National Association of Professional Base Ball Players (NA) was then established as the first professional baseball league. In 1876 six clubs from the NA and two independents joined to create the National League (NL). In subsequent years, the following major leagues competed against the NL, but all eventually folded:
* American Association (AA) (1882–1891) – several franchises transferred to the NL, both during and after the AA's existence.
* Union Association (UA) (1884) – only one franchise joined the NL after the UA disbanded.
* Players' League (PL) (1890) – none of its franchises joined the NL.
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 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. The Kansas City Blues moved to Washington D.C. to play as the Senators.
Another major league competitor was the Federal League (FL) (1914–1915). However, none of its teams joined either the NL or AL after it disbanded.
In 2020, Major League Baseball designated the following seven Negro leagues from 1920–1948 as major leagues:
* Negro National League I (NNL I) (1920–1931)
* Eastern Colored League (ECL) (1923–1928)
* American Negro League (ANL) (1929)
* East–West League (EWL) (1932)
* Negro Southern League (NSL) (1932)
* Negro National League II (NNL II) (1933–1948)
* Negro American League (NAL) (1937–1948)

## Graphical timeline

The first line is the formation of the National League (NL) in 1876, and the second is the transformation of the American League (AL) 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 in 2000.
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.
* Prior to 1876, only teams from the National Association (NA) that established the NL are shown.
* Between 1876 and 1901, in addition to the NL teams, only American Association (AA) and Union Association (UA) teams that eventually joined the NL are shown. No teams from the Players' League (PL) are shown.
* After 1901, only AL and NL teams are shown. No teams from the Federal League (FL) nor the seven Negro leagues are shown.

## 1876–1900: Pre-modern Era
### 1876: Founding of the National League (NL)

The NL was established with eight teams.
* Only season in NL §
1876 National League teams :
| Boston Red Caps | Louisville Grays |
| Chicago White Stockings | New York Mutuals§ |
| Cincinnati Reds | Philadelphia Athletics§ |
| Hartford Dark Blues | St. Louis Brown Stockings |

### 1877

* The New York Mutuals and Philadelphia Athletics were expelled.
* The Hartford Dark Blues moved to Brooklyn and became the Brooklyn Hartfords.
* Team folded after this season ^
1877 National League teams :
| Boston Red Caps | Cincinnati Reds |
| Brooklyn Hartfords^ | Louisville Grays^ |
| Chicago White Stockings | St. Louis Brown Stockings^ |

### 1878

* The Brooklyn Hartfords, Louisville Grays, and St. Louis Brown Stockings folded.
* The Indianapolis Blues, Milwaukee Grays, and Providence Grays joined.
| First season in NL * | Only season in NL § |
1878 National League teams :
| Boston Red Caps | Indianapolis Blues§ |
| Chicago White Stockings | Milwaukee Grays§ |
| Cincinnati Reds | Providence Grays* |

### 1879

* The Indianapolis Blues and Milwaukee Grays folded.
* The Buffalo Bisons, Cleveland Blues, Syracuse Stars, and Troy Trojans joined.
| First season in NL * | Only season in NL § | Team disbanded after this season ^ |
1879 National League teams :
| Boston Red Caps | Cleveland Blues* |
| Buffalo Bisons* | Providence Grays |
| Chicago White Stockings | Syracuse Stars§ |
| Cincinnati Reds^ | Troy Trojans* |

### 1880

* The Syracuse Stars folded.
* The Cincinnati Reds disbanded and were replaced by the Cincinnati Stars.
* The Worcester Worcesters joined.
| First season in NL * | Only season in NL § |
1880 National League teams :
| Boston Red Caps | Cleveland Blues |
| Buffalo Bisons | Providence Grays |
| Chicago White Stockings | Troy Trojans |
| Cincinnati Stars§ | Worcester Worcesters* |

### 1881

* The Cincinnati Stars were expelled because they refused to sign a league-wide pledge to ban alcohol at ballparks.
* The Detroit Wolverines joined.
* First season in NL *
1881 National League teams :
| Boston Red Caps | Detroit Wolverines* |
| Buffalo Bisons | Providence Grays |
| Chicago White Stockings | Troy Trojans |
| Cleveland Blues | Worcester Worcesters |

### 1882: Establishment of the American Association (AA)

The AA was established with six teams.
* Team folded after this season ^
1882 Major League teams :
| NL | AA |
| Boston Red Caps | Baltimore Orioles |
| Buffalo Bisons | Cincinnati Red Stockings |
| Chicago White Stockings | Louisville Eclipse |
| Cleveland Blues | Philadelphia Athletics |
| Detroit Wolverines | Pittsburgh Alleghenys |
| Providence Grays | St. Louis Brown Stockings |
| Troy Trojans^ | |
| Worcester Worcesters^ | |

### 1883

* The Troy Trojans and Worcester Worcesters folded.
* The New York Gothams and Philadelphia Quakers joined the NL.
* The Columbus Buckeyes and New York Metropolitans joined the AA.
* The Boston Red Caps became the Boston Beaneaters.
* The new St. Louis Brown Stockings became the St. Louis Browns.
* First season in NL or AA *
1883 Major League teams :
| NL | AA |
| Boston Beaneaters | Baltimore Orioles |
| Buffalo Bisons | Cincinnati Red Stockings |
| Chicago White Stockings | Columbus Buckeyes* |
| Cleveland Blues | Louisville Eclipse |
| Detroit Wolverines | New York Metropolitans* |
| New York Gothams* | Philadelphia Athletics |
| Philadelphia Quakers* | Pittsburgh Alleghenys |
| Providence Grays | St. Louis Browns |

### 1884: The Union Association (UA) as a third league

* The UA was established with eight teams.
* The Brooklyn Atlantics, Indianapolis Hoosiers, Toledo Blue Stockings, and Washington Nationals joined the AA.
* The Altoona Mountain Citys folded early-season and were replaced by the Kansas City Cowboys.
* The Washington Nationals from the AA folded mid-season and were replaced by the Richmond Virginians from Minor League Baseball.
* The Philadelphia Keystones folded mid-season and were replaced by the Wilmington Quicksteps from Minor League Baseball. The Quicksteps then folded late-season and were replaced by the Milwaukee Brewers, also from Minor League Baseball.
* The Chicago Browns moved to Pittsburgh and became the Pittsburgh Stogies, who folded late-season and were replaced by the St. Paul Saints.
| First season in AA * | Only season in AA/Folds mid-season § | Last season in AA or NL ^ |
1884 Major League teams :
| NL | AA | UA |
| Boston Beaneaters | Baltimore Orioles | Altoona Mountain Citys§ |
| Buffalo Bisons | Brooklyn Atlantics* | Baltimore Monumentals |
| Chicago White Stockings | Cincinnati Red Stockings | Boston Reds |
| Cleveland Blues^ | Columbus Buckeyes^ | Chicago Browns/Pittsburgh Stogies§ |
| Detroit Wolverines | Indianapolis Hoosiers§ | Cincinnati Outlaw Reds |
| New York Gothams | Louisville Eclipse | Kansas City Cowboys |
| Philadelphia Quakers | New York Metropolitans | Milwaukee Brewers |
| Providence Grays | Philadelphia Athletics | Philadelphia Keystones§ |
| | Pittsburgh Alleghenys | St. Louis Maroons |
| | Richmond Virginians§ | St. Paul Saints |
| | St. Louis Browns | Washington Nationals |
| | Toledo Blue Stockings§ | Wilmington Quicksteps§ |
| | Washington Nationals§ | |

### 1885: Back to two leagues

* The UA disbanded.
* The St. Louis Maroons from the UA joined the NL.
* The Cleveland Blues, Columbus Buckeyes, Indianapolis Hoosiers, and Toledo Blue Stockings folded.
* The Richmond Virginians returned to Minor League Baseball.
* The New York Gothams became the New York Giants.
* The Brooklyn Atlantics became the Brooklyn Grays.
* The Louisville Eclipse became the Louisville Colonels.
| Team moved from the former UA ** | Last season in NL ^ |
1885 Major League teams :
| NL | AA |
| Boston Beaneaters | Baltimore Orioles |
| Buffalo Bisons^ | Brooklyn Grays |
| Chicago White Stockings | Cincinnati Red Stockings |
| Detroit Wolverines | Louisville Colonels |
| New York Giants | New York Metropolitans |
| Philadelphia Quakers | Philadelphia Athletics |
| Providence Grays^ | Pittsburgh Alleghenys |
| St. Louis Maroons** | St. Louis Browns |

### 1886

* The Buffalo Bisons transferred to Minor League Baseball.
* The Providence Grays folded.
* A new Kansas City Cowboys and Washington Nationals joined the NL.
| First season in NL * | Only season in NL § |
1886 Major League teams :
| NL | AA |
| Boston Beaneaters | Baltimore Orioles |
| Chicago White Stockings | Brooklyn Grays |
| Detroit Wolverines | Cincinnati Red Stockings |
| Kansas City Cowboys§ | Louisville Colonels |
| New York Giants | New York Metropolitans |
| Philadelphia Quakers | Philadelphia Athletics |
| St. Louis Maroons | Pittsburgh Alleghenys |
| Washington Nationals* | St. Louis Browns |

### 1887

* The Kansas City Cowboys folded.
* The St. Louis Maroons moved to Indianapolis and became the Indianapolis Hoosiers.
* The Pittsburgh Alleghenys transferred to the NL.
* A new Cleveland Blues joined the AA.
| First season in AA * | Team moved from AA ** | Last season in AA ^ |
1887 Major League teams :
| NL | AA |
| Boston Beaneaters | Baltimore Orioles |
| Chicago White Stockings | Brooklyn Grays |
| Detroit Wolverines | Cincinnati Red Stockings |
| Indianapolis Hoosiers | Cleveland Blues* |
| New York Giants | Louisville Colonels |
| Philadelphia Quakers | New York Metropolitans^ |
| Pittsburgh Alleghenys** | Philadelphia Athletics |
| Washington Nationals | St. Louis Browns |

### 1888

* The Brooklyn Grays became the Brooklyn Bridegrooms.
* The New York Metropolitans folded.
* A new Kansas City Cowboys joined the AA.
| First season in AA * | Last season in NL ^ |
1888 Major League teams :
| NL | AA |
| Boston Beaneaters | Baltimore Orioles |
| Chicago White Stockings | Brooklyn Bridegrooms |
| Detroit Wolverines^ | Cincinnati Red Stockings |
| Indianapolis Hoosiers | Cleveland Blues |
| New York Giants | Kansas City Cowboys* |
| Philadelphia Quakers | Louisville Colonels |
| Pittsburgh Alleghenys | Philadelphia Athletics |
| Washington Nationals | St. Louis Browns |

### 1889

* The Detroit Wolverines folded.
* The Cleveland Blues transferred to the NL and became the Cleveland Spiders.
* The Columbus Solons joined the AA.
| First season in AA * | Team moved from AA ** | Last season in AA or NL ^ |
1889 Major League teams :
| NL | AA |
| Boston Beaneaters | Baltimore Orioles |
| Chicago White Stockings | Brooklyn Bridegrooms |
| Cleveland Spiders** | Cincinnati Red Stockings |
| Indianapolis Hoosiers^ | Columbus Solons* |
| New York Giants | Kansas City Cowboys^ |
| Philadelphia Quakers | Louisville Colonels |
| Pittsburgh Alleghenys | Philadelphia Athletics |
| Washington Nationals^ | St. Louis Browns |

### 1890: The Players' League (PL) as a third league

* The PL was established with eight teams.
* The Chicago White Stockings became the Chicago Colts.
* The Philadelphia Quakers became the Philadelphia Phillies.
* The Brooklyn Bridegrooms transferred to the NL.
* 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.
* The Rochester Broncos, a new Syracuse Stars, and the Toledo Maumees joined the AA.
| Team moved from AA ** | Only season in AA § | Last AA season ^ |
1890 Major League teams :
| NL | AA | PL |
| Boston Beaneaters | Baltimore Orioles | Boston Reds |
| Brooklyn Bridegrooms** | Brooklyn Gladiators§ | Brooklyn Ward's Wonders |
| Chicago Colts | Columbus Solons | Buffalo Bisons |
| Cincinnati Reds** | Louisville Colonels | Chicago Pirates |
| Cleveland Spiders | Philadelphia Athletics^ | Cleveland Infants |
| New York Giants | Rochester Broncos§ | New York Giants (PL) |
| Philadelphia Phillies | St. Louis Browns | Philadelphia Athletics (PL) |
| Pittsburgh Alleghenys | Syracuse Stars§ | Pittsburgh Burghers |
| | Toledo Maumees§ | |

### 1891: Last AA season

* The PL disbanded.
* The Brooklyn Bridegrooms became the Brooklyn Grooms.
* The Pittsburgh Alleghenys became the Pittsburgh Pirates.
* The Boston Reds from the PL joined the AA.
* The Philadelphia Athletics from the AA were expelled and replaced by the new Philadelphia Athletics from the PL.
* The Cincinnati Kelly's Killers joined the AA. They then folded mid-season and were replaced by the new Milwaukee Brewers from independent league Western Association.
* The Washington Statesmen joined the AA.
| First MLB season * | Only season in MLB § | Last MLB season ^ |
1891 Major League teams :
| NL | AA |
| Boston Beaneaters | Baltimore Orioles |
| Brooklyn Grooms | Boston Reds^ |
| Chicago Colts | Cincinnati Kelly's Killers§ |
| Cincinnati Reds | Columbus Solons^ |
| Cleveland Spiders | Louisville Colonels |
| New York Giants | Milwaukee Brewers§ |
| Philadelphia Phillies | Philadelphia Athletics^ |
| Pittsburgh Pirates | St. Louis Browns |
| | Washington Statesmen* |

### 1892: NL monopoly

* The AA folded.
* The Baltimore Orioles, Louisville Colonels, St. Louis Browns, and Washington Statesmen (all from the AA) joined the NL.
* The Washington Statesmen became the Washington Senators.
* Teams move from the former AA **
1892 to 1895 National League teams :
| Baltimore Orioles** | Louisville Colonels** |
| Boston Beaneaters | New York Giants |
| Brooklyn Grooms | Philadelphia Phillies |
| Chicago Colts | Pittsburgh Pirates |
| Cincinnati Reds | St. Louis Browns** |
| Cleveland Spiders | Washington Senators** |

### 1896

The Brooklyn Grooms became the Brooklyn Bridegrooms again.
1896 to 1897 National League teams :
| Baltimore Orioles | Louisville Colonels |
| Boston Beaneaters | New York Giants |
| Brooklyn Bridegrooms | Philadelphia Phillies |
| Chicago Colts | Pittsburgh Pirates |
| Cincinnati Reds | St. Louis Browns |
| Cleveland Spiders | Washington Senators |

### 1898

The Chicago Colts became the Chicago Orphans.
1898 National League teams :
| Baltimore Orioles | Louisville Colonels |
| Boston Beaneaters | New York Giants |
| Brooklyn Bridegrooms | Philadelphia Phillies |
| Chicago Orphans | Pittsburgh Pirates |
| Cincinnati Reds | St. Louis Browns |
| Cleveland Spiders | Washington Senators |

### 1899

* The Brooklyn Bridegrooms became the Brooklyn Superbas.
* The St. Louis Browns became the St. Louis Perfectos.
* Team folded after this season ^
1899 National League teams :
| Baltimore Orioles^ | Louisville Colonels^ |
| Boston Beaneaters | New York Giants |
| Brooklyn Superbas | Philadelphia Phillies |
| Chicago Orphans | Pittsburgh Pirates |
| Cincinnati Reds | St. Louis Perfectos |
| Cleveland Spiders^ | Washington Senators^ |

### 1900: Classic Eight

* The Baltimore Orioles, Cleveland Spiders, Louisville Colonels, and Washington Senators folded.
* The St. Louis Perfectos became the St. Louis Cardinals.
1900 National League teams :
| Boston Beaneaters | New York Giants |
| Brooklyn Superbas | Philadelphia Phillies |
| Chicago Orphans | Pittsburgh Pirates |
| Cincinnati Reds | St. Louis Cardinals |

## 1901–1919: Birth of the Modern Era
### 1901: Founding of the American League (AL)

The AL was established with eight teams.
1901 Major League teams :
| AL | NL |
| Baltimore Orioles | Boston Beaneaters |
| Boston Americans | Brooklyn Superbas |
| Chicago White Stockings | Chicago Orphans |
| Cleveland Blues | Cincinnati Reds |
| Detroit Tigers | New York Giants |
| Milwaukee Brewers | Philadelphia Phillies |
| Philadelphia Athletics | Pittsburgh Pirates |
| Washington Senators | St. Louis Cardinals |

### 1902

* The Milwaukee Brewers moved to St. Louis and became the St. Louis Browns.
* The Cleveland Blues became the Cleveland Bronchos
* Team folded after this season ^
1902 Major League teams :
| AL | NL |
| Baltimore Orioles^ | Boston Beaneaters |
| Boston Americans | Brooklyn Superbas |
| Chicago White Stockings | Chicago Orphans |
| Cleveland Bronchos | Cincinnati Reds |
| Detroit Tigers | New York Giants |
| Philadelphia Athletics | Philadelphia Phillies |
| St. Louis Browns | Pittsburgh Pirates |
| Washington Senators | St. Louis Cardinals |

### 1903: National Agreement and Founding of National Baseball Commission

* The NL and AL signed the National Agreement which formed the National Baseball Commission. They then promoted cooperation between the NL and AL.
* The new Baltimore Orioles folded.
* The New York Highlanders joined the AL.
* The Cleveland Bronchos became the Cleveland Naps.
* The Chicago Orphans became the Chicago Cubs.
* First World Series played between the AL and NL champions.
* First AL season *
1903 Major League teams :
| AL | NL |
| Boston Americans | Boston Beaneaters |
| Chicago White Stockings | Brooklyn Superbas |
| Cleveland Naps | Chicago Cubs |
| Detroit Tigers | Cincinnati Reds |
| New York Highlanders* | New York Giants |
| Philadelphia Athletics | Philadelphia Phillies |
| St. Louis Browns | Pittsburgh Pirates |
| Washington Senators | St. Louis Cardinals |

### 1904

The Chicago White Stockings became the Chicago White Sox.
1904 to 1906 Major League teams :
| AL | NL |
| Boston Americans | Boston Beaneaters |
| Chicago White Sox | Brooklyn Superbas |
| Cleveland Naps | Chicago Cubs |
| Detroit Tigers | Cincinnati Reds |
| New York Highlanders | New York Giants |
| Philadelphia Athletics | Philadelphia Phillies |
| St. Louis Browns | Pittsburgh Pirates |
| Washington Senators | St. Louis Cardinals |

### 1907

The Boston Beaneaters became the Boston Doves.
1907 Major League teams :
| AL | NL |
| Boston Americans | Boston Doves |
| Chicago White Sox | Brooklyn Superbas |
| Cleveland Naps | Chicago Cubs |
| Detroit Tigers | Cincinnati Reds |
| New York Highlanders | New York Giants |
| Philadelphia Athletics | Philadelphia Phillies |
| St. Louis Browns | Pittsburgh Pirates |
| Washington Senators | St. Louis Cardinals |

### 1908

The Boston Americans became the Boston Red Sox.
1908 to 1910 Major League teams :
| AL | NL |
| Boston Red Sox | Boston Doves |
| Chicago White Sox | Brooklyn Superbas |
| Cleveland Naps | Chicago Cubs |
| Detroit Tigers | Cincinnati Reds |
| New York Highlanders | New York Giants |
| Philadelphia Athletics | Philadelphia Phillies |
| St. Louis Browns | Pittsburgh Pirates |
| Washington Senators | St. Louis Cardinals |

### 1911

* The Boston Doves became the Boston Rustlers.
* The Brooklyn Superbas became the Brooklyn Trolley Dodgers.
1911 Major League teams :
| AL | NL |
| Boston Red Sox | Boston Rustlers |
| Chicago White Sox | Brooklyn Trolley Dodgers |
| Cleveland Naps | Chicago Cubs |
| Detroit Tigers | Cincinnati Reds |
| New York Highlanders | New York Giants |
| Philadelphia Athletics | Philadelphia Phillies |
| St. Louis Browns | Pittsburgh Pirates |
| Washington Senators | St. Louis Cardinals |

### 1912

The Boston Rustlers became the Boston Braves.
1912 Major League teams :
| AL | NL |
| Boston Red Sox | Boston Braves |
| Chicago White Sox | Brooklyn Trolley Dodgers |
| Cleveland Naps | Chicago Cubs |
| Detroit Tigers | Cincinnati Reds |
| New York Highlanders | New York Giants |
| Philadelphia Athletics | Philadelphia Phillies |
| St. Louis Browns | Pittsburgh Pirates |
| Washington Senators | St. Louis Cardinals |

### 1913

* The New York Highlanders became the New York Yankees.
* The Brooklyn Trolley Dodgers became the Brooklyn Dodgers.
1913 Major League teams :
| AL | NL |
| Boston Red Sox | Boston Braves |
| Chicago White Sox | Brooklyn Dodgers |
| Cleveland Naps | Chicago Cubs |
| Detroit Tigers | Cincinnati Reds |
| New York Yankees | New York Giants |
| Philadelphia Athletics | Philadelphia Phillies |
| St. Louis Browns | Pittsburgh Pirates |
| Washington Senators | St. Louis Cardinals |

### 1914: The Federal League (FL) as a third league

* The Federal League (FL) declared itself as a "third major league" with its own eight teams, and competed with the NL and AL.
* The Brooklyn Dodgers became the Brooklyn Robins.
1914 Major League teams :
| AL | NL | FL |
| Boston Red Sox | Boston Braves | Baltimore Terrapins |
| Chicago White Sox | Brooklyn Robins | Brooklyn Tip-Tops |
| Cleveland Naps | Chicago Cubs | Buffalo Buffeds |
| Detroit Tigers | Cincinnati Reds | Chicago Federals |
| New York Yankees | New York Giants | Indianapolis Hoosiers |
| Philadelphia Athletics | Philadelphia Phillies | Kansas City Packers |
| St. Louis Browns | Pittsburgh Pirates | Pittsburgh Rebels |
| Washington Senators | St. Louis Cardinals | St. Louis Terriers |

### 1915

* The Cleveland Naps became the Cleveland Indians.
* The Buffalo Buffeds became the Buffalo Blues.
* The Chicago Federals became the Chicago Whales.
* The new Indianapolis Hoosiers moved to Newark, New Jersey, and became the Newark Peppers.
1915 Major League teams :
| AL | NL | FL |
| Boston Red Sox | Boston Braves | Baltimore Terrapins |
| Chicago White Sox | Brooklyn Robins | Brooklyn Tip-Tops |
| Cleveland Indians | Chicago Cubs | Buffalo Blues |
| Detroit Tigers | Cincinnati Reds | Chicago Whales |
| New York Yankees | New York Giants | Kansas City Packers |
| Philadelphia Athletics | Philadelphia Phillies | Newark Peppers |
| St. Louis Browns | Pittsburgh Pirates | Pittsburgh Rebels |
| Washington Senators | St. Louis Cardinals | St. Louis Terriers |

### 1916: Back to two leagues

The FL folded prior to the season.
1916 to 1919 Major League teams :
| AL | NL |
| Boston Red Sox | Boston Braves |
| Chicago White Sox | Brooklyn Robins |
| Cleveland Indians | Chicago Cubs |
| Detroit Tigers | Cincinnati Reds |
| New York Yankees | New York Giants |
| Philadelphia Athletics | Philadelphia Phillies |
| St. Louis Browns | Pittsburgh Pirates |
| Washington Senators | St. Louis Cardinals |

## 1920–1946: Establishment of the Negro major leagues
### 1920: Establishment of the Negro National League (NNL)

The NNL was established with eight teams, the first black baseball league to be designated a major league.
* Team withdrew after this season ^^
1920 Major League teams & 1920 Negro Major League teams :
| AL | NL | NNL |
| Boston Red Sox | Boston Braves | Chicago American Giants |
| Chicago White Sox | Brooklyn Robins | Chicago Giants |
| Cleveland Indians | Chicago Cubs | Cuban Stars |
| Detroit Tigers | Cincinnati Reds | Dayton Marcos^^ |
| New York Yankees | New York Giants | Detroit Stars |
| Philadelphia Athletics | Philadelphia Phillies | Indianapolis ABCs |
| St. Louis Browns | Pittsburgh Pirates | Kansas City Monarchs |
| Washington Senators | St. Louis Cardinals | St. Louis Giants |

### 1921: Commissioner of Baseball established

* 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.
* The Dayton Marcos departed the NNL as an independent team.
* A new Columbus Buckeyes joined the NNL.
* The Cuban Stars became the Cincinnati Cuban Stars.
| Only season in NNL § | Team folded after this season ^ |
1921 Major League teams & 1921 Negro Major League teams :
| AL | NL | NNL |
| Boston Red Sox | Boston Braves | Chicago American Giants |
| Chicago White Sox | Brooklyn Robins | Chicago Giants^ |
| Cleveland Indians | Chicago Cubs | Cincinnati Cuban Stars |
| Detroit Tigers | Cincinnati Reds | Columbus Buckeyes§ |
| New York Yankees | New York Giants | Detroit Stars |
| Philadelphia Athletics | Philadelphia Phillies | Indianapolis ABCs |
| St. Louis Browns | Pittsburgh Pirates | Kansas City Monarchs |
| Washington Senators | St. Louis Cardinals | St. Louis Giants |

### 1922

* The Chicago Giants and Columbus Buckeyes folded.
* The Cleveland Tate Stars and Pittsburgh Keystones joined the NNL.
* The Cincinnati Cuban Stars became the Cuban Stars again.
* The St. Louis Giants became the St. Louis Stars.
| First season in NNL * | Only season in NNL § |
1922 Major League teams & 1922 Negro Major League teams :
| AL | NL | NNL |
| Boston Red Sox | Boston Braves | Chicago American Giants |
| Chicago White Sox | Brooklyn Robins | Cleveland Tate Stars* |
| Cleveland Indians | Chicago Cubs | Cuban Stars |
| Detroit Tigers | Cincinnati Reds | Detroit Stars |
| New York Yankees | New York Giants | Indianapolis ABCs |
| Philadelphia Athletics | Philadelphia Phillies | Kansas City Monarchs |
| St. Louis Browns | Pittsburgh Pirates | Pittsburgh Keystones§ |
| Washington Senators | St. Louis Cardinals | St. Louis Stars |

### 1923: Founding of the Eastern Colored League (ECL)

* The ECL was established with six teams.
* The Pittsburgh Keystones folded.
* The Milwaukee Bears joined the NNL.
* 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 Negro Major League teams :
| AL | NL | NNL | ECL |
| Boston Red Sox | Boston Braves | Chicago American Giants | Atlantic City Bacharach Giants |
| Chicago White Sox | Brooklyn Robins | Cuban Stars (West) | Baltimore Black Sox |
| Cleveland Indians | Chicago Cubs | Detroit Stars | Brooklyn Royal Giants |
| Detroit Tigers | Cincinnati Reds | Indianapolis ABCs | Cuban Stars (East) |
| New York Yankees | New York Giants | Kansas City Monarchs | Hilldale Club |
| Philadelphia Athletics | Philadelphia Phillies | Milwaukee Bears§ | New York Lincoln Giants |
| St. Louis Browns | Pittsburgh Pirates | St. Louis Stars | |
| Washington Senators | St. Louis Cardinals | Toledo Tigers§§ | |
| | | Cleveland Tate Stars^ | |

### 1924

* The Milwaukee Bears folded.
* The Birmingham Black Barons and Cleveland Browns joined the NNL.
* The Harrisburg Giants and Washington Potomacs joined the ECL.
* The Indianapolis ABCs temporarily dropped out for the season in June and were replaced by the Memphis Red Sox.
| First season in NNL or ECL* | Only season in NNL § |
1924 Major League teams & 1924 Negro Major League teams :
| AL | NL | NNL | ECL |
| Boston Red Sox | Boston Braves | Birmingham Black Barons* | Atlantic City Bacharach Giants |
| Chicago White Sox | Brooklyn Robins | Chicago American Giants | Baltimore Black Sox |
| Cleveland Indians | Chicago Cubs | Cleveland Browns§ | Brooklyn Royal Giants |
| Detroit Tigers | Cincinnati Reds | Cuban Stars (West) | Cuban Stars (East) |
| New York Yankees | New York Giants | Detroit Stars | Harrisburg Giants* |
| Philadelphia Athletics | Philadelphia Phillies | Indianapolis ABCs | Hilldale Club |
| St. Louis Browns | Pittsburgh Pirates | Kansas City Monarchs | New York Lincoln Giants |
| Washington Senators | St. Louis Cardinals | Memphis Red Sox* | Washington Potomacs* |
| | | St. Louis Stars | |

### 1925

* The Cleveland Browns folded.
* The Indianapolis ABCs returned to the NNL.
* The Washington Potomacs moved to Wilmington, Delaware and became the Wilmington Potomacs and then folded mid-season.
| Team folded mid-season ^ | Team withdrew after this season ^^ |
1925 Major League teams & 1925 Negro Major League teams :
| AL | NL | NNL | ECL |
| Boston Red Sox | Boston Braves | Birmingham Black Barons^^ | Atlantic City Bacharach Giants |
| Chicago White Sox | Brooklyn Robins | Chicago American Giants | Baltimore Black Sox |
| Cleveland Indians | Chicago Cubs | Cuban Stars (West) | Brooklyn Royal Giants |
| Detroit Tigers | Cincinnati Reds | Detroit Stars | Cuban Stars (East) |
| New York Yankees | New York Giants | Indianapolis ABCs | Harrisburg Giants |
| Philadelphia Athletics | Philadelphia Phillies | Kansas City Monarchs | Hilldale Club |
| St. Louis Browns | Pittsburgh Pirates | Memphis Red Sox^^ | New York Lincoln Giants |
| Washington Senators | St. Louis Cardinals | St. Louis Stars | Wilmington Potomacs^ |

### 1926

* The Cleveland Elites joined the NNL and folded mid-season.
* The Dayton Marcos returned to the NNL and departed mid-season as an independent team.
* The Newark Stars joined the ECL and folded mid-season.
* The Birmingham Black Barons and Memphis Red Sox departed the NNL and joined Minor League Baseball's Negro Southern League (NSL).
| Only season in NNL or ECL, folded mid-season § | Team folded after this season ^ | Last season in NNL, withdrew mid-season ^^ |
1926 Major League teams & 1926 Negro Major League teams :
| AL | NL | NNL | ECL |
| Boston Red Sox | Boston Braves | Chicago American Giants | Atlantic City Bacharach Giants |
| Chicago White Sox | Brooklyn Robins | Cleveland Elites§ | Baltimore Black Sox |
| Cleveland Indians | Chicago Cubs | Dayton Marcos^^ | Brooklyn Royal Giants |
| Detroit Tigers | Cincinnati Reds | Cuban Stars (West) | Cuban Stars (East) |
| New York Yankees | New York Giants | Detroit Stars | Harrisburg Giants |
| Philadelphia Athletics | Philadelphia Phillies | Indianapolis ABCs^ | Hilldale Club |
| St. Louis Browns | Pittsburgh Pirates | Kansas City Monarchs | New York Lincoln Giants |
| Washington Senators | St. Louis Cardinals | St. Louis Stars | Newark Stars§ |

### 1927

* The Indianapolis ABCs folded.
* The Birmingham Black Barons and Memphis Red Sox returned to the NNL.
* The Cleveland Hornets joined the NNL.
| Team rejoined from minor league Negro Southern League ** | Only season in NNL § | Last season in NNL or ECL ^ | Team departed after this season ^^ |
1927 Major League teams & 1927 Negro Major League teams :
| AL | NL | NNL | ECL |
| Boston Red Sox | Boston Braves | Birmingham Black Barons** | Atlantic City Bacharach Giants |
| Chicago White Sox | Brooklyn Robins | Chicago American Giants | Baltimore Black Sox |
| Cleveland Indians | Chicago Cubs | Cleveland Hornets§ | Brooklyn Royal Giants^ |
| Detroit Tigers | Cincinnati Reds | Cuban Stars (West) | Cuban Stars (East) |
| New York Yankees | New York Giants | Detroit Stars | Harrisburg Giants^ |
| Philadelphia Athletics | Philadelphia Phillies | Kansas City Monarchs | Hilldale Club^^ |
| St. Louis Browns | Pittsburgh Pirates | Memphis Red Sox** | New York Lincoln Giants |
| Washington Senators | St. Louis Cardinals | St. Louis Stars | |

### 1928: Last ECL season

* The Cleveland Hornets folded.
* The Brooklyn Royal Giants, Harrisburg Giants, and Hilldale Club withdrew from the ECL as independent teams.
* The Cleveland Tigers joined the NNL.
* The Philadelphia Tigers joined the ECL.
* The ECL then disbanded mid-season.
| First season in MLB * | Only season in NNL or ECL § | Last MLB season ^ |
1928 Major League teams & 1928 Negro Major League teams :
| AL | NL | NNL | ECL |
| Boston Red Sox | Boston Braves | Birmingham Black Barons | Atlantic City Bacharach Giants |
| Chicago White Sox | Brooklyn Robins | Chicago American Giants | Baltimore Black Sox |
| Cleveland Indians | Chicago Cubs | Cleveland Tigers§ | Cuban Stars (East) |
| Detroit Tigers | Cincinnati Reds | Cuban Stars (West) | New York Lincoln Giants |
| New York Yankees | New York Giants | Detroit Stars | Philadelphia Tigers§ |
| Philadelphia Athletics | Philadelphia Phillies | Kansas City Monarchs | |
| St. Louis Browns | Pittsburgh Pirates | Memphis Red Sox | |
| Washington Senators | St. Louis Cardinals | St. Louis Stars | |

### 1929: American Negro League (ANL)'s only season

* The ANL was established with six teams. Five of those teams were from the ECL. The independent Homestead Grays also joined the ECL.
* The Cleveland Tigers folded.
* The Philadelphia Tigers folded.
| Team folded after this season ^ | Team independent after this season ^^ |
1929 Major League teams & 1929 Negro Major League teams :
| AL | NL | NNL | ANL |
| Boston Red Sox | Boston Braves | Birmingham Black Barons | Atlantic City Bacharach Giants^ |
| Chicago White Sox | Brooklyn Robins | Chicago American Giants | Baltimore Black Sox^^ |
| Cleveland Indians | Chicago Cubs | Cuban Stars (West) | Cuban Stars (East)^ |
| Detroit Tigers | Cincinnati Reds | Detroit Stars | Hilldale Club^^ |
| New York Yankees | New York Giants | Kansas City Monarchs | Homestead Grays^^ |
| Philadelphia Athletics | Philadelphia Phillies | Memphis Red Sox | New York Lincoln Giants^^ |
| St. Louis Browns | Pittsburgh Pirates | St. Louis Stars | |
| Washington Senators | St. Louis Cardinals | | |

### 1930

* The Atlantic City Bacharach Giants and the Cuban Stars from the ANL folded.
* The Baltimore Black Sox, Hilldale Club, Homestead Grays, and New York Lincoln Giants became independent teams.
* The ANL disbanded.
* The Louisville Black Caps and Nashville Elite Giants joined the NNL.
| First season in NNL * | Team folded after this season ^ | Team departed after this season ^^ |
1930 Major League teams & 1930 Negro Major League teams :
| AL | NL | NNL |
| Boston Red Sox | Boston Braves | Birmingham Black Barons^^ |
| Chicago White Sox | Brooklyn Robins | Chicago American Giants |
| Cleveland Indians | Chicago Cubs | Cuban Stars^ |
| Detroit Tigers | Cincinnati Reds | Detroit Stars |
| New York Yankees | New York Giants | Kansas City Monarchs^^ |
| Philadelphia Athletics | Philadelphia Phillies | Louisville Black Caps* |
| St. Louis Browns | Pittsburgh Pirates | Memphis Red Sox^^ |
| Washington Senators | St. Louis Cardinals | Nashville Elite Giants* |
| | | St. Louis Stars |

### 1931: Last NNL season

* The Cuban Stars folded.
* The Birmingham Black Barons, Memphis Red Sox, and Nashville Elite Giants departed the NNL and joined the NSL.
* The Kansas City Monarchs departed the NNL as an independent team (though remains loosely associated with the league).
* The Cleveland Cubs and a new Indianapolis ABCs joined the NNL.
* The Chicago American Giants became the Chicago Columbia Giants.
* The Louisville Black Caps became the Louisville White Sox.
* The NNL disbanded mid-season; although, teams continued to play each other as independent teams.
| First season in NNL * | Team folded after this season ^ |
1931 Major League teams & 1931 Negro Major League teams :
| AL | NL | NNL |
| Boston Red Sox | Boston Braves | Chicago Columbia Giants |
| Chicago White Sox | Brooklyn Robins | Cleveland Cubs |
| Cleveland Indians | Chicago Cubs | Detroit Stars^ |
| Detroit Tigers | Cincinnati Reds | Indianapolis ABCs* |
| New York Yankees | New York Giants | Louisville White Sox |
| Philadelphia Athletics | Philadelphia Phillies | St. Louis Stars^ |
| St. Louis Browns | Pittsburgh Pirates | |
| Washington Senators | St. Louis Cardinals | |

### 1932: Negro Southern League (NSL)'s only major league season and East–West League (EWL)'s only season

* The Brooklyn Robins became the Brooklyn Dodgers again.
* The Detroit Stars and St. Louis Stars folded.
* The Cleveland Cubs moved back to Nashville, Tennessee and became the Nashville Elite Giants again.
* The EWL was established with eight teams. Three of those teams, the Baltimore Black Sox, Hilldale Club, and Homestead Grays were from the ANL.
* The NSL was considered a major league for the season with 10 teams. Five of those teams, the Birmingham Black Barons, Chicago Columbia Giants, Indianapolis ABCs, Memphis Red Sox, and Nashville Elite Giants were from the NNL.
* The Chicago Columbia Giants became the Chicago American Giants again.
* The Newark Browns departed mid-season as an independent team.
| Team rejoined MLB ** | Only season in MLB § | Team folded after this season ^ | Team departed after this season ^^ |
1932 Major League teams & 1932 Negro Major League teams :
| AL | NL | NSL | EWL |
| Boston Red Sox | Boston Braves | Atlanta Black Crackers^^ | Baltimore Black Sox** |
| Chicago White Sox | Brooklyn Dodgers | Birmingham Black Barons^^ | Cleveland Stars§ |
| Cleveland Indians | Chicago Cubs | Chicago American Giants** | Detroit Wolves§ |
| Detroit Tigers | Cincinnati Reds | Indianapolis ABCs** | Hilldale Club^ |
| New York Yankees | New York Giants | Little Rock Grays§ | Homestead Grays^^ |
| Philadelphia Athletics | Philadelphia Phillies | Louisville Black Caps/Columbus Turf Club^ | Newark Browns§ |
| St. Louis Browns | Pittsburgh Pirates | Memphis Red Sox^^ | Pollock's Cuban Stars§ |
| Washington Senators | St. Louis Cardinals | Monroe Monarchs§ | Washington Pilots§ |
| | | Montgomery Grey Sox§ | |
| | | Nashville Elite Giants** | |

### 1933: Establishment of the second NNL

* The Little Rock Grays and Columbus Turf Club folded.
* The Atlanta Black Crackers and Birmingham Black Barons withdrew as independent teams.
* The NSL was demoted to minor league status.
* The Cleveland Stars, Detroit Wolves, Hilldale Club, and Newark Browns folded.
* Pollock's Cuban Stars and the Washington Pilots withdrew as independent teams.
* The Baltimore Black Sox became the Baltimore Sox.
* The EWL disbanded.
* The second NNL was established with 7 teams. Five of those teams, the Baltimore Sox, Chicago American Giants, Homestead Grays, Indianapolis ABCs, and Nashville Elite Giants were from the NSL or EWL.
* The Pittsburgh Crawfords joined the NNL.
* The Indianapolis ABCs moved mid-season to Detroit, Michigan and became the Detroit Stars.
* 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 Negro Major League teams :
| AL | NL | NNL |
| Boston Red Sox | Boston Braves | Akron Grays/Cleveland Giants§§^ |
| Chicago White Sox | Brooklyn Dodgers | Baltimore Sox** |
| Cleveland Indians | Chicago Cubs | Chicago American Giants** |
| Detroit Tigers | Cincinnati Reds | Columbus Blue Birds§ |
| New York Yankees | New York Giants | Homestead Grays^^ |
| Philadelphia Athletics | Philadelphia Phillies | Indianapolis ABCs/Detroit Stars^ |
| St. Louis Browns | Pittsburgh Pirates | Nashville Elite Giants** |
| Washington Senators | St. Louis Cardinals | Pittsburgh Crawfords* |

### 1934

* The Cleveland Giants and Detroit Stars folded.
* The Homestead Grays withdrew as an independent team.
* The Cleveland Red Sox, Newark Dodgers, Philadelphia Bacharach Giants, and Philadelphia Stars joined the NNL.
* The Baltimore Sox became the Baltimore Black Sox again.
| First season in NNL * | Only season in NNL § | Team folded after this season ^ |
1934 Major League teams & 1934 Negro Major League teams :
| AL | NL | NNL |
| Boston Red Sox | Boston Braves | Baltimore Black Sox^ |
| Chicago White Sox | Brooklyn Dodgers | Chicago American Giants |
| Cleveland Indians | Chicago Cubs | Cleveland Red Sox§ |
| Detroit Tigers | Cincinnati Reds | Nashville Elite Giants |
| New York Yankees | New York Giants | Newark Dodgers* |
| Philadelphia Athletics | Philadelphia Phillies | Philadelphia Bacharach Giants§ |
| St. Louis Browns | Pittsburgh Pirates | Philadelphia Stars* |
| Washington Senators | St. Louis Cardinals | Pittsburgh Crawfords |

### 1935

* The Cleveland Red Sox folded.
* The Baltimore Black Sox and Philadelphia Bacharach Giants withdrew as independent teams.
* The Brooklyn Eagles and New York Cubans joined the NNL.
* The Homestead Grays returned to the NNL.
* The Nashville Elite Giants moved to Columbus, Ohio and became the Columbus Elite Giants.
| First season in NNL * | Team rejoined MLB ** | Only season in NNL § | Team folded after this season ^ | Team departed after this season ^^ |
1935 Major League teams & 1935 Negro Major League teams :
| AL | NL | NNL |
| Boston Red Sox | Boston Braves | Brooklyn Eagles§ |
| Chicago White Sox | Brooklyn Dodgers | Chicago American Giants^^ |
| Cleveland Indians | Chicago Cubs | Columbus Elite Giants |
| Detroit Tigers | Cincinnati Reds | Homestead Grays** |
| New York Yankees | New York Giants | New York Cubans* |
| Philadelphia Athletics | Philadelphia Phillies | Newark Dodgers^ |
| St. Louis Browns | Pittsburgh Pirates | Philadelphia Stars |
| Washington Senators | St. Louis Cardinals | Pittsburgh Crawfords |

### 1936

* The Boston Braves became the Boston Bees.
* The Chicago American Giants withdrew.
* The Brooklyn Eagles and Newark Dodgers merged and became the Newark Eagles.
* The New York Black Yankees joined the NNL.
* The Columbus Elite Giants moved to Washington, D.C. and became the Washington Elite Giants.
| First season in NNL * | Team departed after this season ^^ |
1936 Major League teams & 1936 Negro Major League teams :
| AL | NL | NNL |
| Boston Red Sox | Boston Bees | Homestead Grays |
| Chicago White Sox | Brooklyn Dodgers | New York Black Yankees* |
| Cleveland Indians | Chicago Cubs | New York Cubans^^ |
| Detroit Tigers | Cincinnati Reds | Newark Eagles* |
| New York Yankees | New York Giants | Philadelphia Stars |
| Philadelphia Athletics | Philadelphia Phillies | Pittsburgh Crawfords |
| St. Louis Browns | Pittsburgh Pirates | Washington Elite Giants |
| Washington Senators | St. Louis Cardinals | |

### 1937: Founding of the Negro American League (NAL)

* The NAL was established with eight teams. Four of those teams, the Birmingham Black Barons, Chicago American Giants, Kansas City Monarchs, and Memphis Red Sox were previously from the NSL or the first NNL.
* The New York Cubans withdrew.
| Team rejoined MLB ** | Only season in NAL § |
1937 Major League teams & 1937 Negro Major League teams :
| AL | NL | NAL | NNL |
| Boston Red Sox | Boston Bees | Birmingham Black Barons** | Homestead Grays |
| Chicago White Sox | Brooklyn Dodgers | Chicago American Giants** | New York Black Yankees |
| Cleveland Indians | Chicago Cubs | Cincinnati Tigers§ | Newark Eagles |
| Detroit Tigers | Cincinnati Reds | Detroit Stars§ | Philadelphia Stars |
| New York Yankees | New York Giants | Indianapolis Athletics§ | Pittsburgh Crawfords |
| Philadelphia Athletics | Philadelphia Phillies | Kansas City Monarchs** | Washington Elite Giants |
| St. Louis Browns | Pittsburgh Pirates | Memphis Red Sox** | |
| Washington Senators | St. Louis Cardinals | St. Louis Stars§ | |

### 1938

* The Cincinnati Tigers, the new Detroit Stars, the Indianapolis Athletics, and the new St. Louis Stars folded.
* The Atlanta Black Crackers, a new Indianapolis ABCs, and the Jacksonville Red Caps joined the NAL.
* The Washington Black Senators joined the NNL.
* The Washington Elite Giants moved to Baltimore, Maryland and became the Baltimore Elite Giants.
| First season in NAL * | Team rejoined MLB ** | Only season in NNL § | Team departed after this season ^^ |
1938 Major League teams & 1938 Negro Major League teams :
| AL | NL | NAL | NNL |
| Boston Red Sox | Boston Bees | Atlanta Black Crackers** | Baltimore Elite Giants |
| Chicago White Sox | Brooklyn Dodgers | Birmingham Black Barons^^ | Homestead Grays |
| Cleveland Indians | Chicago Cubs | Chicago American Giants | New York Black Yankees |
| Detroit Tigers | Cincinnati Reds | Indianapolis ABCs* | Newark Eagles |
| New York Yankees | New York Giants | Jacksonville Red Caps* | Philadelphia Stars |
| Philadelphia Athletics | Philadelphia Phillies | Kansas City Monarchs | Pittsburgh Crawfords |
| St. Louis Browns | Pittsburgh Pirates | Memphis Red Sox | Washington Black Senators§ |
| Washington Senators | St. Louis Cardinals | | |

### 1939

* The Washington Black Senators folded.
* The Birmingham Black Barons withdrew.
* The New York Cubans returned to the NNL.
* The Indianapolis ABCs moved to St. Louis, Missouri and became the St. Louis Stars.
* The Atlanta Black Crackers moved to Indianapolis, Indiana and became the Indianapolis ABCs.
* The Jacksonville Red Caps moved to Cleveland, Ohio and became the Cleveland Bears.
* The Pittsburgh Crawfords moved to Toledo, Ohio and became the Toledo Crawfords.
* The Toledo Crawfords withdrew and joined the NAL mid-season.
| Team joined NAL or rejoined NNL ** | Team folded after this season ^ | Team left NNL mid-season ^^ |
1939 Major League teams & 1939 Negro Major League teams :
| AL | NL | NAL | NNL |
| Boston Red Sox | Boston Bees | Chicago American Giants | Baltimore Elite Giants |
| Chicago White Sox | Brooklyn Dodgers | Cleveland Bears | Homestead Grays |
| Cleveland Indians | Chicago Cubs | Indianapolis ABCs^ | New York Black Yankees |
| Detroit Tigers | Cincinnati Reds | Kansas City Monarchs | New York Cubans** |
| New York Yankees | New York Giants | Memphis Red Sox | Newark Eagles |
| Philadelphia Athletics | Philadelphia Phillies | St. Louis Stars | Philadelphia Stars |
| St. Louis Browns | Pittsburgh Pirates | Toledo Crawfords** | Toledo Crawfords^^ |
| Washington Senators | St. Louis Cardinals | | |

### 1940

* The Indianapolis ABCs folded.
* The Birmingham Black Barons returned to the NAL.
* The St. Louis Stars split their home games between St. Louis, Missouri and New Orleans, Louisiana and became the St. Louis–New Orleans Stars.
* The Toledo Crawfords split their home games between Toledo, Ohio and Indianapolis, Indiana and became the Toledo–Indianapolis Crawfords.
| Team rejoined NAL ** | Team folded after this season ^ |
1940 Major League teams & 1940 Negro Major League teams :
| AL | NL | NAL | NNL |
| Boston Red Sox | Boston Bees | Birmingham Black Barons** | Baltimore Elite Giants |
| Chicago White Sox | Brooklyn Dodgers | Chicago American Giants | Homestead Grays |
| Cleveland Indians | Chicago Cubs | Cleveland Bears | New York Black Yankees |
| Detroit Tigers | Cincinnati Reds | Kansas City Monarchs | New York Cubans |
| New York Yankees | New York Giants | Memphis Red Sox | Newark Eagles |
| Philadelphia Athletics | Philadelphia Phillies | St. Louis–New Orleans Stars | Philadelphia Stars |
| St. Louis Browns | Pittsburgh Pirates | Toledo–Indianapolis Crawfords^ | |
| Washington Senators | St. Louis Cardinals | | |

### 1941

* The Boston Bees became the Boston Braves again.
* The Toledo–Indianapolis Crawfords folded.
* The Cleveland Bears moved back to Jacksonville, Florida and became the Jacksonville Red Caps again.
* Team temporarily folded after this season ^^
1941 Major League teams & 1941 Negro Major League teams :
| AL | NL | NAL | NNL |
| Boston Red Sox | Boston Braves | Birmingham Black Barons | Baltimore Elite Giants |
| Chicago White Sox | Brooklyn Dodgers | Chicago American Giants | Homestead Grays |
| Cleveland Indians | Chicago Cubs | Jacksonville Red Caps | New York Black Yankees |
| Detroit Tigers | Cincinnati Reds | Kansas City Monarchs | New York Cubans |
| New York Yankees | New York Giants | Memphis Red Sox | Newark Eagles |
| Philadelphia Athletics | Philadelphia Phillies | St. Louis–New Orleans Stars^^ | Philadelphia Stars |
| St. Louis Browns | Pittsburgh Pirates | | |
| Washington Senators | St. Louis Cardinals | | |

### 1942

* The Philadelphia Phillies became the Philadelphia Phils.
* The St. Louis–New Orleans Stars disbanded.
* The Cincinnati–Cleveland Buckeyes joined the NAL.
* The Jacksonville Red Caps departed mid-season.
| First season in NAL * | Team left mid-season ^ |
1942 Major League teams & 1942 Negro Major League teams :
| AL | NL | NAL | NNL |
| Boston Red Sox | Boston Braves | Birmingham Black Barons | Baltimore Elite Giants |
| Chicago White Sox | Brooklyn Dodgers | Chicago American Giants | Homestead Grays |
| Cleveland Indians | Chicago Cubs | Cincinnati–Cleveland Buckeyes* | New York Black Yankees |
| Detroit Tigers | Cincinnati Reds | Jacksonville Red Caps^ | New York Cubans |
| New York Yankees | New York Giants | Kansas City Monarchs | Newark Eagles |
| Philadelphia Athletics | Philadelphia Phils | Memphis Red Sox | Philadelphia Stars |
| St. Louis Browns | Pittsburgh Pirates | | |
| Washington Senators | St. Louis Cardinals | | |

### 1943

* The Philadelphia Phils became the Philadelphia Phillies again.
* 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.
* The Cincinnati–Cleveland Buckeyes left Cincinnati, Ohio and became the Cleveland Buckeyes.
* The Cincinnati Clowns joined the NAL.
| First season in NAL * | Team folds mid-season ^ |
1943 Major League teams & 1943 Negro Major League teams :
| AL | NL | NAL | NNL |
| Boston Red Sox | Boston Braves | Birmingham Black Barons | Baltimore Elite Giants |
| Chicago White Sox | Brooklyn Dodgers | Chicago American Giants | Harrisburg–St. Louis Stars^ |
| Cleveland Indians | Chicago Cubs | Cincinnati Clowns* | Homestead Grays |
| Detroit Tigers | Cincinnati Reds | Cleveland Buckeyes | New York Black Yankees |
| New York Yankees | New York Giants | Kansas City Monarchs | New York Cubans |
| Philadelphia Athletics | Philadelphia Phillies | Memphis Red Sox | Newark Eagles |
| St. Louis Browns | Pittsburgh Pirates | | Philadelphia Stars |
| Washington Senators | St. Louis Cardinals | | |

### 1944

The Cincinnati Clowns split their home games between Cincinnati, Ohio and Indianapolis, Indiana and became the Cincinnati–Indianapolis Clowns, though would play more games in Indianapolis beginning in 1946.
1944 to 1946 Major League teams & 1944 to 1946 Negro Major League teams :
| AL | NL | NAL | NNL |
| Boston Red Sox | Boston Braves | Birmingham Black Barons | Baltimore Elite Giants |
| Chicago White Sox | Brooklyn Dodgers | Chicago American Giants | Homestead Grays |
| Cleveland Indians | Chicago Cubs | Cincinnati–Indianapolis Clowns | New York Black Yankees |
| Detroit Tigers | Cincinnati Reds | Cleveland Buckeyes | New York Cubans |
| New York Yankees | New York Giants | Kansas City Monarchs | Newark Eagles |
| Philadelphia Athletics | Philadelphia Phillies | Memphis Red Sox | Philadelphia Stars |
| St. Louis Browns | Pittsburgh Pirates | | |
| Washington Senators | St. Louis Cardinals | | |

## 1947–1960: Integration, end of the Negro major leagues, and relocations
### 1947

The Brooklyn Dodgers, Cleveland Indians, and St. Louis Browns integrated.
* Team has yet to integrate †
1947 Major League teams & 1947 major Negro league teams :
| AL | NL | NAL | NNL |
| Boston Red Sox† | Boston Braves† | Birmingham Black Barons | Baltimore Elite Giants |
| Chicago White Sox† | Brooklyn Dodgers | Chicago American Giants | Homestead Grays |
| Cleveland Indians | Chicago Cubs† | Cleveland Buckeyes | New York Black Yankees |
| Detroit Tigers† | Cincinnati Reds† | Cincinnati–Indianapolis Clowns | New York Cubans |
| New York Yankees† | New York Giants† | Kansas City Monarchs | Newark Eagles |
| Philadelphia Athletics† | Philadelphia Phillies† | Memphis Red Sox | Philadelphia Stars |
| St. Louis Browns | Pittsburgh Pirates† | | |
| Washington Senators† | St. Louis Cardinals† | | |

### 1948

| Team has yet to integrate † | Team folded after this season ^ |
* The Cincinnati–Indianapolis Clowns stopped playing in Cincinnati, Ohio and permanently played in Indianapolis, Indiana and became the Indianapolis Clowns.
1948 Major League teams & 1948 major Negro league teams :
| AL | NL | NAL | NNL |
| Boston Red Sox† | Boston Braves† | Birmingham Black Barons | Baltimore Elite Giants |
| Chicago White Sox† | Brooklyn Dodgers | Chicago American Giants | Homestead Grays |
| Cleveland Indians | Chicago Cubs† | Cleveland Buckeyes | New York Black Yankees^ |
| Detroit Tigers† | Cincinnati Reds† | Indianapolis Clowns | New York Cubans |
| New York Yankees† | New York Giants† | Kansas City Monarchs | Newark Eagles |
| Philadelphia Athletics† | Philadelphia Phillies† | Memphis Red Sox | Philadelphia Stars |
| St. Louis Browns | Pittsburgh Pirates† | | |
| Washington Senators† | St. Louis Cardinals† | | |

### 1949

* The New York Black Yankees folded.
* Due to the ongoing process of integration, the NAL lost its major league status.
* The NNL folded.
* All of the NNL teams, except for the newly independent Homestead Grays joined the NAL.
* The New York Giants integrated.
* Team has yet to integrate †
1949 Major League teams :
| AL | NL |
| Boston Red Sox† | Boston Braves† |
| Chicago White Sox† | Brooklyn Dodgers |
| Cleveland Indians | Chicago Cubs† |
| Detroit Tigers† | Cincinnati Reds† |
| New York Yankees† | New York Giants |
| Philadelphia Athletics† | Philadelphia Phillies† |
| St. Louis Browns | Pittsburgh Pirates† |
| Washington Senators† | St. Louis Cardinals† |

### 1950

The Boston Braves integrated.
* Team has yet to integrate †
1950 Major League teams :
| AL | NL |
| Boston Red Sox† | Boston Braves |
| Chicago White Sox† | Brooklyn Dodgers |
| Cleveland Indians | Chicago Cubs† |
| Detroit Tigers† | Cincinnati Reds† |
| New York Yankees† | New York Giants |
| Philadelphia Athletics† | Philadelphia Phillies† |
| St. Louis Browns | Pittsburgh Pirates† |
| Washington Senators† | St. Louis Cardinals† |

### 1951

The Chicago White Sox integrated.
* Team has yet to integrate †
1951 to 1952 Major League teams :
| AL | NL |
| Boston Red Sox† | Boston Braves |
| Chicago White Sox | Brooklyn Dodgers |
| Cleveland Indians | Chicago Cubs† |
| Detroit Tigers† | Cincinnati Reds† |
| New York Yankees† | New York Giants |
| Philadelphia Athletics† | Philadelphia Phillies† |
| St. Louis Browns | Pittsburgh Pirates† |
| Washington Senators† | St. Louis Cardinals† |

### 1953: Braves relocation to Milwaukee, and Cincinnati renaming

* The Boston Braves moved to Milwaukee and became the Milwaukee Braves.
* The Cincinnati Reds became the Cincinnati Redlegs.
* The Chicago Cubs, Philadelphia Athletics, and Pittsburgh Pirates integrated.
* Team has yet to integrate †
1953 Major League teams :
| AL | NL |
| Boston Red Sox† | Brooklyn Dodgers |
| Chicago White Sox | Chicago Cubs |
| Cleveland Indians | Cincinnati Redlegs† |
| Detroit Tigers† | Milwaukee Braves |
| New York Yankees† | New York Giants |
| Philadelphia Athletics | Philadelphia Phillies† |
| St. Louis Browns | Pittsburgh Pirates |
| Washington Senators† | St. Louis Cardinals† |

### 1954: Browns relocation to Baltimore

* The St. Louis Browns moved to Baltimore and became the Baltimore Orioles.
* The Cincinnati Redlegs, St. Louis Cardinals, and Washington Senators integrated.
* Team has yet to integrate †
1954 Major League teams :
| AL | NL |
| Baltimore Orioles | Brooklyn Dodgers |
| Boston Red Sox† | Chicago Cubs |
| Chicago White Sox | Cincinnati Redlegs |
| Cleveland Indians | Milwaukee Braves |
| Detroit Tigers† | New York Giants |
| New York Yankees† | Philadelphia Phillies† |
| Philadelphia Athletics | Pittsburgh Pirates |
| Washington Senators | St. Louis Cardinals |

### 1955: Athletics relocation to Kansas City

* The Philadelphia Athletics moved to Kansas City, Missouri, and became the Kansas City Athletics.
* The New York Yankees integrated.
* Team has yet to integrate †
1955 to 1956 Major League teams :
| AL | NL |
| Baltimore Orioles | Brooklyn Dodgers |
| Boston Red Sox† | Chicago Cubs |
| Chicago White Sox | Cincinnati Redlegs |
| Cleveland Indians | Milwaukee Braves |
| Detroit Tigers† | New York Giants |
| Kansas City Athletics | Philadelphia Phillies† |
| New York Yankees | Pittsburgh Pirates |
| Washington Senators | St. Louis Cardinals |

### 1957

The Philadelphia Phillies integrated.
* Team has yet to integrate †
1957 Major League teams :
| AL | NL |
| Baltimore Orioles | Brooklyn Dodgers |
| Boston Red Sox† | Chicago Cubs |
| Chicago White Sox | Cincinnati Redlegs |
| Cleveland Indians | Milwaukee Braves |
| Detroit Tigers† | New York Giants |
| Kansas City Athletics | Philadelphia Phillies |
| New York Yankees | Pittsburgh Pirates |
| Washington Senators | St. Louis Cardinals |

### 1958: The NL exits New York for California

* The Brooklyn Dodgers moved to Los Angeles and became the Los Angeles Dodgers.
* The New York Giants moved to San Francisco and became the San Francisco Giants.
* The Detroit Tigers integrated.
* Team has yet to integrate †
1958 Major League teams :
| AL | NL |
| Baltimore Orioles | Chicago Cubs |
| Boston Red Sox† | Cincinnati Redlegs |
| Chicago White Sox | Los Angeles Dodgers |
| Cleveland Indians | Milwaukee Braves |
| Detroit Tigers | Philadelphia Phillies |
| Kansas City Athletics | Pittsburgh Pirates |
| New York Yankees | St. Louis Cardinals |
| Washington Senators | San Francisco Giants |

### 1959: Cincinnati reverts back to the Reds

* The Cincinnati Redlegs became the Cincinnati Reds again.
* The Boston Red Sox integrated.
1959 to 1960 Major League teams :
| AL | NL |
| Baltimore Orioles | Chicago Cubs |
| Boston Red Sox | Cincinnati Reds |
| Chicago White Sox | Los Angeles Dodgers |
| Cleveland Indians | Milwaukee Braves |
| Detroit Tigers | Philadelphia Phillies |
| Kansas City Athletics | Pittsburgh Pirates |
| New York Yankees | St. Louis Cardinals |
| Washington Senators | San Francisco Giants |

## 1961–1968: First expansion
### 1961 Relocation and AL expansion

* The Washington Senators moved to the Minneapolis–Saint Paul area and became the Minnesota Twins.
* The Los Angeles Angels and a new Washington Senators joined the AL.
* 1961 expansion team *
1961 Major League teams :
| AL | NL |
| Baltimore Orioles | Chicago Cubs |
| Boston Red Sox | Cincinnati Reds |
| Chicago White Sox | Los Angeles Dodgers |
| Cleveland Indians | Milwaukee Braves |
| Detroit Tigers | Philadelphia Phillies |
| Kansas City Athletics | Pittsburgh Pirates |
| Los Angeles Angels* | St. Louis Cardinals |
| Minnesota Twins | San Francisco Giants |
| New York Yankees | |
| Washington Senators* | |

### 1962: NL expansion

* The Houston Colt .45s and New York Mets joined the NL.
* 1962 expansion team *
1962 to 1964 Major League teams :
| AL | NL |
| Baltimore Orioles | Chicago Cubs |
| Boston Red Sox | Cincinnati Reds |
| Chicago White Sox | Houston Colt .45s* |
| Cleveland Indians | Los Angeles Dodgers |
| Detroit Tigers | Milwaukee Braves |
| Kansas City Athletics | New York Mets* |
| Los Angeles Angels | Philadelphia Phillies |
| Minnesota Twins | Pittsburgh Pirates |
| New York Yankees | St. Louis Cardinals |
| Washington Senators | San Francisco Giants |

### 1965: Houston and Angels renaming

* The Houston Colt .45s became the Houston Astros.
* The Los Angeles Angels became the California Angels on September 2, 1965, with 28 games left in the season.
1965 Major League teams :
| AL | NL |
| Baltimore Orioles | Chicago Cubs |
| Boston Red Sox | Cincinnati Reds |
| Los Angeles/California Angels | Houston Astros |
| Chicago White Sox | Los Angeles Dodgers |
| Cleveland Indians | Milwaukee Braves |
| Detroit Tigers | New York Mets |
| Kansas City Athletics | Philadelphia Phillies |
| Minnesota Twins | Pittsburgh Pirates |
| New York Yankees | St. Louis Cardinals |
| Washington Senators | San Francisco Giants |

### 1966: Braves relocation to Atlanta

The Milwaukee Braves moved to Atlanta and became the Atlanta Braves.
1966 to 1967 Major League teams :
| AL | NL |
| Baltimore Orioles | Atlanta Braves |
| Boston Red Sox | Chicago Cubs |
| California Angels | Cincinnati Reds |
| Chicago White Sox | Houston Astros |
| Cleveland Indians | Los Angeles Dodgers |
| Detroit Tigers | New York Mets |
| Kansas City Athletics | Philadelphia Phillies |
| Minnesota Twins | Pittsburgh Pirates |
| New York Yankees | St. Louis Cardinals |
| Washington Senators | San Francisco Giants |

### 1968: Athletics relocation to Oakland

The Kansas City Athletics moved to Oakland, California, and became the Oakland Athletics.
1968 Major League teams :
| AL | NL |
| Baltimore Orioles | Atlanta Braves |
| Boston Red Sox | Chicago Cubs |
| California Angels | Cincinnati Reds |
| Chicago White Sox | Houston Astros |
| Cleveland Indians | Los Angeles Dodgers |
| Detroit Tigers | New York Mets |
| Minnesota Twins | Philadelphia Phillies |
| New York Yankees | Pittsburgh Pirates |
| Oakland Athletics | St. Louis Cardinals |
| Washington Senators | San Francisco Giants |

## 1969–1993: Birth of division play
### 1969: Expansion and realignment

* The Kansas City Royals and Seattle Pilots joined the AL.
* The Montreal Expos and San Diego Padres joined the NL.
* The two leagues each realigned into two six-team divisions
* 1969 expansion team *
1969 Major League teams :
| AL | AL | NL | NL |
| East | West | East | West |
| Baltimore Orioles | California Angels | Chicago Cubs | Atlanta Braves |
| Boston Red Sox | Chicago White Sox | Montreal Expos* | Cincinnati Reds |
| Cleveland Indians | Kansas City Royals* | New York Mets | Houston Astros |
| Detroit Tigers | Minnesota Twins | Philadelphia Phillies | Los Angeles Dodgers |
| New York Yankees | Oakland Athletics | Pittsburgh Pirates | San Diego Padres* |
| Washington Senators | Seattle Pilots* | St. Louis Cardinals | San Francisco Giants |

### 1970: Pilots relocation to Milwaukee

The Seattle Pilots moved to Milwaukee and became the Milwaukee Brewers.
1970 to 1971 Major League teams :
| AL | AL | NL | NL |
| East | West | East | West |
| Baltimore Orioles | California Angels | Chicago Cubs | Atlanta Braves |
| Boston Red Sox | Chicago White Sox | Montreal Expos | Cincinnati Reds |
| Cleveland Indians | Kansas City Royals | New York Mets | Houston Astros |
| Detroit Tigers | Milwaukee Brewers | Philadelphia Phillies | Los Angeles Dodgers |
| New York Yankees | Minnesota Twins | Pittsburgh Pirates | San Diego Padres |
| Washington Senators | Oakland Athletics | St. Louis Cardinals | San Francisco Giants |

### 1972: Senators relocation to the Dallas–Fort Worth metroplex

* The Washington Senators moved to Arlington, Texas, in the Dallas–Fort Worth metroplex and became the Texas Rangers.
* The Texas Rangers and Milwaukee Brewers switched divisions.
1972 to 1976 Major League teams :
| AL | AL | NL | NL |
| East | West | East | West |
| Baltimore Orioles | California Angels | Chicago Cubs | Atlanta Braves |
| Boston Red Sox | Chicago White Sox | Montreal Expos | Cincinnati Reds |
| Cleveland Indians | Kansas City Royals | New York Mets | Houston Astros |
| Detroit Tigers | Minnesota Twins | Philadelphia Phillies | Los Angeles Dodgers |
| Milwaukee Brewers | Oakland Athletics | Pittsburgh Pirates | San Diego Padres |
| New York Yankees | Texas Rangers | St. Louis Cardinals | San Francisco Giants |

### 1977: AL expansion

* The Seattle Mariners joined the AL West.
* The Toronto Blue Jays joined the AL East.
* 1977 expansion team *
1977 to 1992 Major League teams :
| AL | AL | NL | NL |
| East | West | East | West |
| Baltimore Orioles | California Angels | Chicago Cubs | Atlanta Braves |
| Boston Red Sox | Chicago White Sox | Montreal Expos | Cincinnati Reds |
| Cleveland Indians | Kansas City Royals | New York Mets | Houston Astros |
| Detroit Tigers | Minnesota Twins | Philadelphia Phillies | Los Angeles Dodgers |
| Milwaukee Brewers | Oakland Athletics | Pittsburgh Pirates | San Diego Padres |
| New York Yankees | Seattle Mariners* | St. Louis Cardinals | San Francisco Giants |
| Toronto Blue Jays* | Texas Rangers | | |

### 1993: NL expansion

* The Colorado Rockies joined the NL West.
* The Florida Marlins joined the NL East.
* 1993 expansion team *
1993 Major League teams :
| AL | AL | NL | NL |
| East | West | East | West |
| Baltimore Orioles | California Angels | Chicago Cubs | Atlanta Braves |
| Boston Red Sox | Chicago White Sox | Florida Marlins* | Cincinnati Reds |
| Cleveland Indians | Kansas City Royals | Montreal Expos | Colorado Rockies* |
| Detroit Tigers | Minnesota Twins | New York Mets | Houston Astros |
| Milwaukee Brewers | Oakland Athletics | Philadelphia Phillies | Los Angeles Dodgers |
| New York Yankees | Seattle Mariners | Pittsburgh Pirates | San Diego Padres |
| Toronto Blue Jays | Texas Rangers | St. Louis Cardinals | San Francisco Giants |

## 1994–present: Wild Card era
### 1994: Realignment

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.
* The Atlanta Braves transferred to the NL East.
1994 to 1996 Major League teams :
| AL | AL | AL | NL | NL | NL |
| East | Central | West | East | Central | West |
| Baltimore Orioles | Chicago White Sox | California Angels | Atlanta Braves | Chicago Cubs | Colorado Rockies |
| Boston Red Sox | Cleveland Indians | Oakland Athletics | Florida Marlins | Cincinnati Reds | Los Angeles Dodgers |
| Detroit Tigers | Kansas City Royals | Seattle Mariners | Montreal Expos | Houston Astros | San Diego Padres |
| New York Yankees | Milwaukee Brewers | Texas Rangers | New York Mets | Pittsburgh Pirates | San Francisco Giants |
| Toronto Blue Jays | Minnesota Twins | | Philadelphia Phillies | St. Louis Cardinals | |

### 1997: Angels renaming

The California Angels became the Anaheim Angels.
1997 Major League teams :
| AL | AL | AL | NL | NL | NL |
| East | Central | West | East | Central | West |
| Baltimore Orioles | Chicago White Sox | Anaheim Angels | Atlanta Braves | Chicago Cubs | Colorado Rockies |
| Boston Red Sox | Cleveland Indians | Oakland Athletics | Florida Marlins | Cincinnati Reds | Los Angeles Dodgers |
| Detroit Tigers | Kansas City Royals | Seattle Mariners | Montreal Expos | Houston Astros | San Diego Padres |
| New York Yankees | Milwaukee Brewers | Texas Rangers | New York Mets | Pittsburgh Pirates | San Francisco Giants |
| Toronto Blue Jays | Minnesota Twins | | Philadelphia Phillies | St. Louis Cardinals | |

### 1998: Expansion

* The Arizona Diamondbacks joined the NL West.
* The Tampa Bay Devil Rays joined the AL East.
* The Detroit Tigers transferred to the AL Central.
* 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.
* 1998 expansion team *
1998 to 1999 Major League teams :
| AL | AL | AL | NL | NL | NL |
| East | Central | West | East | Central | West |
| Baltimore Orioles | Chicago White Sox | Anaheim Angels | Atlanta Braves | Chicago Cubs | Arizona Diamondbacks* |
| Boston Red Sox | Cleveland Indians | Oakland Athletics | Florida Marlins | Cincinnati Reds | Colorado Rockies |
| New York Yankees | Detroit Tigers | Seattle Mariners | Montreal Expos | Houston Astros | Los Angeles Dodgers |
| Tampa Bay Devil Rays* | Kansas City Royals | Texas Rangers | New York Mets | Milwaukee Brewers | San Diego Padres |
| Toronto Blue Jays | Minnesota Twins | | Philadelphia Phillies | Pittsburgh Pirates | San Francisco Giants |
| | | | | St. Louis Cardinals | |

### 2000: Legal merger of AL & NL into MLB

* The AL and NL merged and formed Major League Baseball.
2000 to 2004 Major League Baseball teams :
| AL | AL | AL | NL | NL | NL |
| East | Central | West | East | Central | West |
| Baltimore Orioles | Chicago White Sox | Anaheim Angels | Atlanta Braves | Chicago Cubs | Arizona Diamondbacks |
| Boston Red Sox | Cleveland Indians | Oakland Athletics | Florida Marlins | Cincinnati Reds | Colorado Rockies |
| New York Yankees | Detroit Tigers | Seattle Mariners | Montreal Expos | Houston Astros | Los Angeles Dodgers |
| Tampa Bay Devil Rays | Kansas City Royals | Texas Rangers | New York Mets | Milwaukee Brewers | San Diego Padres |
| Toronto Blue Jays | Minnesota Twins | | Philadelphia Phillies | Pittsburgh Pirates | San Francisco Giants |
| | | | | St. Louis Cardinals | |

### 2001: Scrapped contraction to 28 teams

In 2001, MLB team owners voted 28–2 to eliminate two teams, the Minnesota Twins and the Montreal Expos for the 2002 season. In this realignment:
* Texas Rangers would move to the AL Central
* Arizona Diamondbacks would move to the AL West
* Pittsburgh Pirates would move to the NL East
Planned league realignment for the 2002 Major League Baseball season :
| AL | AL | AL | NL | NL | NL |
| East | Central | West | East | Central | West |
| Baltimore Orioles | Chicago White Sox | Anaheim Angels | Atlanta Braves | Chicago Cubs | Colorado Rockies |
| Boston Red Sox | Cleveland Indians | Arizona Diamondbacks | Florida Marlins | Cincinnati Reds | Los Angeles Dodgers |
| New York Yankees | Detroit Tigers | Oakland Athletics | New York Mets | Houston Astros | San Diego Padres |
| Tampa Bay Devil Rays | Kansas City Royals | Seattle Mariners | Philadelphia Phillies | Milwaukee Brewers | San Francisco Giants |
| Toronto Blue Jays | Texas Rangers | | Pittsburgh Pirates | St. Louis Cardinals | |
By December 2001, this plan was scrapped; both teams would be retained for the following season.

### 2005: Expos relocation and Angels renaming

* The Montreal Expos moved to Washington, D.C. and became the Washington Nationals.
* The Anaheim Angels became the Los Angeles Angels of Anaheim.
2005 to 2007 Major League Baseball teams :
| AL | AL | AL | NL | NL | NL |
| East | Central | West | East | Central | West |
| Baltimore Orioles | Chicago White Sox | Los Angeles Angels of Anaheim | Atlanta Braves | Chicago Cubs | Arizona Diamondbacks |
| Boston Red Sox | Cleveland Indians | Oakland Athletics | Florida Marlins | Cincinnati Reds | Colorado Rockies |
| New York Yankees | Detroit Tigers | Seattle Mariners | New York Mets | Houston Astros | Los Angeles Dodgers |
| Tampa Bay Devil Rays | Kansas City Royals | Texas Rangers | Philadelphia Phillies | Milwaukee Brewers | San Diego Padres |
| Toronto Blue Jays | Minnesota Twins | | Washington Nationals | Pittsburgh Pirates | San Francisco Giants |
| | | | | St. Louis Cardinals | |

### 2008: Tampa Bay renaming

The Tampa Bay Devil Rays became the Tampa Bay Rays.
2008 to 2011 Major League Baseball teams :
| AL | AL | AL | NL | NL | NL |
| East | Central | West | East | Central | West |
| Baltimore Orioles | Chicago White Sox | Los Angeles Angels of Anaheim | Atlanta Braves | Chicago Cubs | Arizona Diamondbacks |
| Boston Red Sox | Cleveland Indians | Oakland Athletics | Florida Marlins | Cincinnati Reds | Colorado Rockies |
| New York Yankees | Detroit Tigers | Seattle Mariners | New York Mets | Houston Astros | Los Angeles Dodgers |
| Tampa Bay Rays | Kansas City Royals | Texas Rangers | Philadelphia Phillies | Milwaukee Brewers | San Diego Padres |
| Toronto Blue Jays | Minnesota Twins | | Washington Nationals | Pittsburgh Pirates | San Francisco Giants |
| | | | | St. Louis Cardinals | |

### 2012: Marlins renaming

The Florida Marlins became the Miami Marlins.
2012 Major League Baseball teams :
| AL | AL | AL | NL | NL | NL |
| East | Central | West | East | Central | West |
| Baltimore Orioles | Chicago White Sox | Los Angeles Angels of Anaheim | Atlanta Braves | Chicago Cubs | Arizona Diamondbacks |
| Boston Red Sox | Cleveland Indians | Oakland Athletics | Miami Marlins | Cincinnati Reds | Colorado Rockies |
| New York Yankees | Detroit Tigers | Seattle Mariners | New York Mets | Houston Astros | Los Angeles Dodgers |
| Tampa Bay Rays | Kansas City Royals | Texas Rangers | Philadelphia Phillies | Milwaukee Brewers | San Diego Padres |
| Toronto Blue Jays | Minnesota Twins | | Washington Nationals | Pittsburgh Pirates | San Francisco Giants |
| | | | | St. Louis Cardinals | |

### 2013: Astros switch leagues

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.
2013 to 2015 Major League Baseball teams :
| AL | AL | AL | NL | NL | NL |
| East | Central | West | East | Central | West |
| Baltimore Orioles | Chicago White Sox | Houston Astros | Atlanta Braves | Chicago Cubs | Arizona Diamondbacks |
| Boston Red Sox | Cleveland Indians | Los Angeles Angels of Anaheim | Miami Marlins | Cincinnati Reds | Colorado Rockies |
| New York Yankees | Detroit Tigers | Oakland Athletics | New York Mets | Milwaukee Brewers | Los Angeles Dodgers |
| Tampa Bay Rays | Kansas City Royals | Seattle Mariners | Philadelphia Phillies | Pittsburgh Pirates | San Diego Padres |
| Toronto Blue Jays | Minnesota Twins | Texas Rangers | Washington Nationals | St. Louis Cardinals | San Francisco Giants |

### 2016: Angels renaming

The Los Angeles Angels of Anaheim became the Los Angeles Angels.
2016 to 2021 Major League Baseball teams :
| AL | AL | AL | NL | NL | NL |
| East | Central | West | East | Central | West |
| Baltimore Orioles | Chicago White Sox | Houston Astros | Atlanta Braves | Chicago Cubs | Arizona Diamondbacks |
| Boston Red Sox | Cleveland Indians | Los Angeles Angels | Miami Marlins | Cincinnati Reds | Colorado Rockies |
| New York Yankees | Detroit Tigers | Oakland Athletics | New York Mets | Milwaukee Brewers | Los Angeles Dodgers |
| Tampa Bay Rays | Kansas City Royals | Seattle Mariners | Philadelphia Phillies | Pittsburgh Pirates | San Diego Padres |
| Toronto Blue Jays | Minnesota Twins | Texas Rangers | Washington Nationals | St. Louis Cardinals | San Francisco Giants |

### 2022: Cleveland renaming

The Cleveland Indians became the Cleveland Guardians.
2022 to 2024 Major League Baseball teams :
| AL | AL | AL | NL | NL | NL |
| East | Central | West | East | Central | West |
| Baltimore Orioles | Chicago White Sox | Houston Astros | Atlanta Braves | Chicago Cubs | Arizona Diamondbacks |
| Boston Red Sox | Cleveland Guardians | Los Angeles Angels | Miami Marlins | Cincinnati Reds | Colorado Rockies |
| New York Yankees | Detroit Tigers | Oakland Athletics | New York Mets | Milwaukee Brewers | Los Angeles Dodgers |
| Tampa Bay Rays | Kansas City Royals | Seattle Mariners | Philadelphia Phillies | Pittsburgh Pirates | San Diego Padres |
| Toronto Blue Jays | Minnesota Twins | Texas Rangers | Washington Nationals | St. Louis Cardinals | San Francisco Giants |

### 2025: Athletics relocation

The Oakland Athletics temporarily moved to West Sacramento, California, and branded themselves as simply the "Athletics" and "A's" with no city name attached, until they permanently relocate to Las Vegas in 2028 or later when their new ballpark is completed.
2025 to present Major League Baseball teams :
| AL | AL | AL | NL | NL | NL |
| East | Central | West | East | Central | West |
| Baltimore Orioles | Chicago White Sox | Athletics | Atlanta Braves | Chicago Cubs | Arizona Diamondbacks |
| Boston Red Sox | Cleveland Guardians | Houston Astros | Miami Marlins | Cincinnati Reds | Colorado Rockies |
| New York Yankees | Detroit Tigers | Los Angeles Angels | New York Mets | Milwaukee Brewers | Los Angeles Dodgers |
| Tampa Bay Rays | Kansas City Royals | Seattle Mariners | Philadelphia Phillies | Pittsburgh Pirates | San Diego Padres |
| Toronto Blue Jays | Minnesota Twins | Texas Rangers | Washington Nationals | St. Louis Cardinals | San Francisco Giants |