OOTP's historical module is designed to where the pre-1901 major leagues are
plausible but not actually historical. This is because - unlike from 1901 on - MLB in the 1800's was very unstable: lots of contraction & expansion from year to year, and so forth, and coding for this would likely be difficult... So OOTP creates a somewhat more stable pre-1901 MLB, with both the AL & NL existing from the beginning... And I say somewhat because there are a bunch of franchise moves and expansions, but there are no franchises that fold...
Here's what you get to start with in 1871:
American League
Boston Red Stockings
Cleveland Forest Citys
Philadelphia Athletics
Washington Olympics
National League
Chicago White Stockings
Fort Wayne Kekiongas
New York Mutuals
Rockford Forest Citys
Troy Haymakers
OOTP's original 9 teams above then evolve as follows:
- Boston Red Stockings > nickname change to Red Caps (1876) > move to NL (1882) > nickname change to Beaneaters (1883) thru 1906 & at that point the history follows that of the team becomes the Boston/Milwaukee/Atlanta Braves
- Cleveland Forest Citys > becomes Elizabeth Resolutes for 1873 > then the Hartford Dark Blues (1874) > Milwaukee Grays (1878) > Cleveland Blues (1879) St Louis Maroons in NL (1885) > Cleveland Blues in the AL (1887) > Spiders (1889), Blues (1901) and then follows the history of the Cleveland franchise that exists today
- Philadelphia Athletics > Louisville Colonels (1892) > Philadelphia Athletics (1901)...
- Washington Olympics > Blue Legs (1873) < Nationals (1875) > Syracuse Stars (1879) > Worcester Ruby Legs (1880) > Columbus Buckeyes (1883) > Washington Nationals (1884) > Buffalo Bisons (1885) > Washington Nationals (1886) > Syracuse Stars (1890) > Washington Statesmen (1891) > Senators (1892)... Minnesota Twins (1961)
- Chicago White Stockings > Middletown Mansfields (1872) > Baltimore Marylands (1873) > Chicago White Stockings (1874) > Colts (1890), Orphans (1898), Cubs (1903)...
- Fort Wayne Kekiongas > Brooklyn Atlantics (1872) > Louisville Grays (1876) > Buffalo Bisons (1879) > Brooklyn Atlantics (1884) > Grays (1885) > Bridegrooms (1888) > Grooms (1891) > Bridegrooms (1896), Superbas (1899) & eventually the Dodgers...
- New York Mutuals > Gothams (1883) > Giants (1885)... & eventually the SF Giants
- Rockford Forest Citys > Baltimore Canaries (1872) > New Haven Elm Citys (1875) > Cincinnati Reds (1876) > Red Stockings (1882) > Reds (1890)...
- Troy Haymakers > Philadelphia Whites (1873) > Troy Trojans (1879) > Philadelphia Quakers (1883) > Philadelphia Phillies (1890)...
OOTP pre-1901 expands as follows:
- 1872, AL: Brooklyn Eckfords > Keokuk Westerns (1880) > Detroit Wolverines (1881) > Columbus Solons (1889) > Milwaukee Brewers (1891) > Detroit Tigers (1901)...
- 1872, NL: Washington Nationals > Philadelphia Centennials (1875) > Pittsburgh Alleghenys (1882) > Pittsburgh Pirates (1891)...
- 1875, AL: St. Louis Brown Stockings > Browns (1883) > Milwaukee Brewers (1901) > St Louis Browns (1902)... eventually Baltimore Orioles...
- 1875, NL: St. Louis Red Stockings > Providence Grays (1878) > Kansas City Cowboys (1886) > Indianapolis Hoosiers (1887) > Kansas City Cowboys (1888) > Brooklyn Gladiators (1890)> Louisville Colonels (1891) > St. Louis Cardinals (1892) > Perfectos (1899) > Cardinals (1900)...
- 1882, AL, Baltimore Orioles > New York Highlanders (1903)... Yankees
- 1882, AL, Louisville Eclipse > Colonels (1885) > Boston Reds (1891) > Americans (1901) > Red Sox (1908)...
- 1883, AL, New York Metropolitans > Indianapolis Hoosiers (1888) > Rochester Broncos (1890) > Columbus Solons (1891) > Chicago White Sox (1901)...
For whatever reason OOTP has an uneven number of teams until 1883, when it evens the AL with the NL at 8 teams each...
Here are a couple threads you might interesting/informative:
https://forums.ootpdevelopments.com/...d.php?t=354248
https://forums.ootpdevelopments.com/....php?p=5056560