September 23 – The Chicago Cubs and New York Giants, involved in a tight pennant race, (also involving the Pittsburgh Pirates) were tied in the bottom of the ninth inning at the Polo Grounds in New York. The Giants had runners on first and third and two outs when Al Bridwell hit a single to center field, scoring Moose McCormick from third with the Giants’ apparent winning run, but the runner on first base, rookie Fred Merkle, thinking the game was over, went half way to second and then sprinted to the clubhouse after McCormick touched home plate. As fans swarmed the field, Cub infielder Johnny Evers retrieved the ball and touched second. A forceout was called at second base, nullifying the single, and because there were 2 outs when the play started, the run was also nullified and the inning ended. The game was declared a tie and would be made up at the end of the season if the Cubs and Giants were tied for first place. The incident became known as the "Merkle Boner".
October 2 – In a game involving the Cleveland Naps and the Chicago White Sox, Ed Walsh struck out 15 Naps and walked one batter, pitching a complete game, but it was not enough as Addie Joss pitched a perfect game, and the Naps beat the White Sox, 1–0, during the heat of a pennant race. Cleveland center fielder Joe Birmingham scored the game's only run. It is perhaps the finest pitching duel in baseball history.