The 1903 World Series was the first modern World Series to be played in Major League Baseball. It matched the Boston Americans (now the Red Sox) of the American League against the Pittsburgh Pirates of the National League in a best-of-nine series, with Boston prevailing five games to three.

In the series, Boston came back from a three games to one deficit, winning the final four games to capture the title. Such a large comeback would not happen again until the Pirates came back to defeat the Washington Senators in the 1925 World Series. Much was made of the influence of Boston's "Royal Rooters", who traveled to Exposition Park and sang their theme song "Tessie" to distract the opposing players, especially Honus Wagner. Boston wound up winning three out of four games in Allegheny City.

Pirates owner Barney Dreyfuss added his share of the gate receipts to the players' share, so the losing team's players actually finished with a larger individual share than the winning team's.

The Series brought the new American League prestige and proved its best could beat the best of the National League, thus strengthening the demand for future World Series competitions.

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