I created a universe that has four major baseball leagues and try to play a version of it in each new edition of OOTP.
AL, NL, PCL and CL
In the NL:
Brooklyn got their domed stadium and stayed put
NY Giants moved to Minnesota
Braves stayed in Milwaukee (usually)
In the AL:
Griffith sold the Senators and the team stayed in DC
A's moved from Kansas City to Atlanta.
AL put an expansion team in Kansas City called the Monarchs after A's moved.
PCL became an outlaw third major league in the 1950s. Was frozen out of World Series play every season despite challenging the AL and NL.
Oakland Oaks
San Francisco Seals
Los Angeles Angels (built Angels Stadium in Chavez Ravine)
California (Hollywood) Stars (built a ballpark and play in Anaheim)
Portland Beavers
Seattle Rainiers
Sacramento Solons
San Diego Padres
Branch Rickey's Continental League became a thing for the 1961 season
New York Metropolitans
Buffalo Bisons
Toronto Maple Leafs
Montreal Royals
Memphis Blues
Dallas Rangers
Denver Rockies
Houston Colts
PCL and CL reached an agreement and began playing their own version of the WS in 1963.
Baseball peace was finally reached and a new national agreement was negotiated in time for the 1972 season, with all four leagues participating in a common postseason playoff culminating in the World Series.
In my mind, THIS is how history should have gone!!!