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Why did the American League and National League compete in the early 1900s?

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Freddie Freeman of the Los Angeles Dodgers, wearing a white uniform and helmet, watches his hit while holding a bat during a game at Dodger Stadium. — Baseball Freddie Freeman, shown here in a 2023 game, was named World Series MVP in 2024 after hitting four home runs and driving in 12 runs for the Los Angeles Dodgers.

The competition between the National League (NL) and the American League (AL) in the early 1900s, often referred to as the "baseball war," arose from a territorial dispute over league expansion.1

The conflict began when the Western League, which had been renamed the American League and elevated to major league status in 1901, sought to place teams in cities like Baltimore and Washington, D.C. The National League, which had previously operated as a monopoly, refused to grant permission for these moves, leading to open hostility. During this period, the American League actively recruited many of the National League's star players to bolster its rosters.1

This rivalry concluded with a peace agreement in 1903, which established rules for player transfers, prohibited single ownership of two clubs in the same city, and required mutual permission for franchise relocation. This resolution led to the creation of the World Series, an annual championship contest between the winners of the two leagues.123