In 1910, he was 4th in the NL in doubles (35) and slugging percentage (.441).
In 1915, he was 6th in the NL in batting (.299).
In the bottom of the 9th inning, Merkle came to bat with two outs, and the score tied 1-1. At the time, Moose McCormick was on first base. Merkle singled and McCormick advanced to third base. Al Bridwell, the next batter, followed with a single of his own. McCormick advanced to home plate scoring the winning run for the game. The fans in attendance, under the impression that the game was over, ran onto the field to celebrate.
Meanwhile, Merkle, thinking the game was over, walked to the Giants' clubhouse without touching second base. Cubs second baseman Johnny Evers noticed this, and after retrieving a ball and touching second base he appealed to umpire Hank O'Day, who would later manage the Cubs, to call Merkle out. Since Merkle had not touched the base, the umpire called him out on a force play, and McCormick's run did not count.
The run was therefore nullified, the Giants' victory erased, and the score of the game remained tied. Unfortunately, the thousands of fans on the field (as well as the growing darkness in the days before large electric light rigs made night games possible) prevented resumption of the game and the game was declared a tie. The Giants and the Cubs would end the season tied for first place and would have a rematch at the Polo Grounds, on October 8. The Cubs won this makeup game, 4-2, and thus the National League pennant.
At the time, running off the field without touching the base was common, as the rule allowing a force play after a potential game-winning run was not well-known. However, Evers, who was noted as an avid student of the official rules of the game, had previously attempted the same play only a few weeks earlier, in Pittsburgh, ironically with the same Hank O'Day umpiring. In that instance, O'Day had not seen whether the runner tagged second, so he declined Evers' appeal, but he apparently was alert to the possibility in the New York game. The outcome ensured that the rule was known to everyone afterward.
His nephew, Theodore Charles Merkle, directed Project Pluto, his grandniece, Judith Merkle Riley, is a historical writer, and his grandnephew, Ralph C. Merkle, is a Distinguished Professor in Computer Science at Georgia Institute of Technology.