Other baseball leagues in 1903:    
Negro
The first World Series was played as an arrangement between the owners of Boston and Pittsburgh clubs rather than a formal arrangement between the two leagues.

AL

TEAMWLPctGB
y 1903 Boston Americans LogoBos. Americans   9147.659-
1903 Philadelphia Athletics LogoPhil. A's 7560.55614.5
1903 Cleveland Naps LogoCleveland 7763.55015.0
1903 New York Highlanders LogoNY Highlanders 7262.53717.0
1903 Detroit Tigers LogoDetroit 6571.47825.0
1903 St. Louis Browns LogoStL Browns 6574.46826.5
1903 Chicago White Sox LogoChi. White Sox 6077.43830.5
1903 Washington Senators LogoWashington 4394.31447.5

NL

y 1903 Pittsburg Pirates LogoPittsburg 9149.650-
1903 New York Giants LogoNY Giants 8455.6046.5
1903 Chicago Cubs LogoChi. Cubs 8256.5948.0
1903 Cincinnati Reds LogoCincinnati 7465.53216.5
1903 Brooklyn Superbas LogoBrooklyn 7066.51519.0
1903 Boston Beaneaters LogoBos. Beaneaters 5880.42032.0
1903 Philadelphia Phillies LogoPhil. Phillies 4986.36339.5
1903 St. Louis Cardinals LogoStL Cardinals 4394.31446.5