Until 1920, in the last of the ninth inning or in the bottom of an extra inning, home runs that drove in the winning run ahead of them were scored only as singles, doubles, or triples, according to how many bases the baserunner needed to advance to score the winning run. For example, if the batter hit a home run in the bottom of the ninth inning with a teammate on third base and the score tied, the batter was credited with only a single. Under current rules, the batter would be credited with a "walk-off" home run and the home team would win by two runs.
In 1918 Babe Ruth hit a "home run" with a teammate on first base in the bottom of the ninth inning of a tied game. Under the rules of the day, Ruth was credited with a triple.
In 1968 the Special Baseball Records Committee voted to restore home runs to players who had lost credit for them because of the above-mentioned pre-1920 rule. But even people in power tinker with baseball's traditions and statistics at great peril. After a hyper-decibel outcry by casual and serious fans, the committee changed its mind in 1969.