Here's a not-so-realistic alternate history idea similar to the one I posted for the NFL. Basically, once the American and National Leagues made "peace" for 1903, they merged and realigned geographically, while retaining their separate league names:

AL: Boston, Boston, Brooklyn, New York, New York, Philadelphia, Philadelphia, Washington
NL: Chicago, Chicago, Cincinnati, Cleveland, Detroit, Pittsburgh, St. Louis, St. Louis

Then after half a century and a variety of nickname changes (source for names), the league looks like this before relocations begin in 1953:

AL: Boston Braves, Boston Red Sox, Brooklyn Dodgers, New York Giants, New York Yankees, Philadelphia Athletics, Philadelphia Phillies, Washington Nationals
NL: Chicago Cubs, Chicago White Sox, Cincinnati Reds, Cleveland Indians, Detroit Tigers, Pittsburgh Pirates, St. Louis Browns, St. Louis Cardinals

They maintain a geographic alignment throughout the expansions and relocations that would ensue:

1953: Boston Braves (AL) to Milwaukee Braves (NL); Cincinnati Reds to Cincinnati Redlegs (remain in NL); Pittsburgh Pirates from NL to AL
1954: St. Louis Browns to Baltimore Orioles (remain in NL)
1955: Philadelphia Athletics (AL) to Kansas City Athletics (NL); Baltimore Orioles from NL to AL
1957: Washington Nationals to Washington Senators (remain in AL)
1958: Brooklyn Dodgers (AL) to Los Angeles Dodgers (NL); New York Giants (AL) to San Francisco Giants (NL); Cincinnati Redlegs and Cleveland Indians from NL to AL
1959: Cincinnati Redlegs to Cincinnati Reds (remain in AL)
1961: Washington Senators (AL) to Minnesota Twins (NL); Los Angeles Angels join NL; (new) Washington Senators join AL; Detroit Tigers from NL to AL
1962: Houston Colt .45s join NL; New York Mets join AL
1965: Houston Colt .45s to Houston Astros (remain in NL); Los Angeles Angels to California Angels (remain in NL)
1966: Milwaukee Braves to Atlanta Braves (remain in NL)
1968: Kansas City Athletics to Oakland Athletics (remain in NL)

Here's what the league looks like before the expansion of 1969 and the advent of divisions:

AL: Baltimore Orioles, Boston Red Sox, Cincinnati Reds, Cleveland Indians, Detroit Tigers, New York Mets, New York Yankees, Philadelphia Phillies, Pittsburgh Pirates, Washington Senators
NL: Atlanta Braves, California Angels, Chicago Cubs, Chicago White Sox, Houston Astros, Los Angeles Dodgers, Minnesota Twins, Oakland Athletics, San Francisco Giants, St. Louis Cardinals

And in 1969:

AL East: Baltimore Orioles, Boston Red Sox, Montreal Expos, New York Mets, New York Yankees, Philadelphia Phillies
AL West: Atlanta Braves, Cincinnati Reds, Cleveland Indians, Detroit Tigers, Pittsburgh Pirates, Washington Senators

NL East: Chicago Cubs, Chicago White Sox, Houston Astros, Kansas City Royals, Minnesota Twins, St. Louis Cardinals
NL West: California Angels, Los Angeles Dodgers, Oakland Athletics, San Diego Padres, San Francisco Giants, Seattle Pilots

Expansion and relocation resume at a much more modest pace:

1970: Seattle Pilots to Milwaukee Brewers (remain in NL West)
1972: Washington Senators (AL West) to Texas Rangers (NL West); Milwaukee Brewers from NL West to AL West
1977: Seattle Mariners join NL West; Toronto Blue Jays join AL East; Texas Rangers from NL West to NL East
1993: Colorado Rockies join NL West; Florida Marlins join AL West

Before another realignment in 1994:

AL North: Boston Red Sox, Montreal Expos, New York Mets, New York Yankees, Toronto Blue Jays
AL South: Atlanta Braves, Baltimore Orioles, Florida Marlins, Philadelphia Phillies
AL West: Cincinnati Reds, Cleveland Indians, Detroit Tigers, Milwaukee Brewers, Pittsburgh Pirates

NL North: Chicago Cubs, Chicago White Sox, Kansas City Royals, Minnesota Twins, St. Louis Cardinals
NL South: Colorado Rockies, Houston Astros, San Diego Padres, Texas Rangers
NL West: California Angels, Los Angeles Dodgers, Oakland Athletics, San Francisco Giants, Seattle Mariners

At which point the game continues:

1997: California Angels to Anaheim Angels (remain in NL West)
1998: Arizona Diamondbacks join NL South; Tampa Bay Devil Rays join AL South
2005: Anaheim Angels to Los Angeles Angels of Anaheim (remain in NL West); Montreal Expos (AL North) to Washington Nationals (AL South); Philadelphia Phillies from AL South to AL North
2008: Tampa Bay Devil Rays to Tampa Bay Rays (remain in AL South)
2012: Florida Marlins to Miami Marlins (remain in AL South)
2016: Los Angeles Angels of Anaheim to Los Angeles Angels (remain in NL West)
2022: Cleveland Indians to Cleveland Guardians (remain in AL West)
2025: Oakland Athletics to Athletics (remain in NL West)

Leading to the present day alignment:

AL North: Boston Red Sox, New York Mets, New York Yankees, Philadelphia Phillies, Toronto Blue Jays
AL South: Atlanta Braves, Baltimore Orioles, Miami Marlins, Tampa Bay Rays, Washington Nationals
AL West: Cincinnati Reds, Cleveland Guardians, Detroit Tigers, Milwaukee Brewers, Pittsburgh Pirates

NL North: Chicago Cubs, Chicago White Sox, Kansas City Royals, Minnesota Twins, St. Louis Cardinals
NL South: Arizona Diamondbacks, Colorado Rockies, Houston Astros, San Diego Padres, Texas Rangers
NL West: Athletics, Los Angeles Angels, Los Angeles Dodgers, San Francisco Giants, Seattle Mariners

Assuming the Athletics wind up in Las Vegas as planned, they'll swap divisions with the Padres.

Are you aware of any historical discussion on this occurring? This would have probably required a true merger of the two leagues then and there.

I think it would have been weird having 2 teams in Boston, Philadelphia, Chicago, and St Louis (and 3 in NYC) playing regularly. I think the stronger teams in those multi-club towns would have ran their weaker crosstown rivals out of town. Those spares probably find their way to places like Baltimore, Buffalo, Milwaukee, & KC.

(07-12-2025 08:27 PM)Fighting Muskie Wrote:  Are you aware of any historical discussion on this occurring? This would have probably required a true merger of the two leagues then and there.

I think it would have been weird having 2 teams in Boston, Philadelphia, Chicago, and St Louis (and 3 in NYC) playing regularly. I think the stronger teams in those multi-club towns would have ran their weaker crosstown rivals out of town. Those spares probably find their way to places like Baltimore, Buffalo, Milwaukee, & KC.

No, nothing historical. But I think that's effectively what happened despite the lack of regular season crosstown play. The first teams to relocate in the '50s were the weaker clubs in Boston, St. Louis, and Philadelphia, to Milwaukee, Baltimore, and KC, respectively.