MLB Single-Season On-Base Percentage Record Progression

Year	Player	OBP	Stood for
2004	Barry Bonds	.609	still standing
2002	Barry Bonds	.582	2 years
1943	JG Josh Gibson	.564	59 years
1941	Ted Williams	.553	2 years
1929	CS Charlie Smith	.550	12 years
1899	John McGraw	.548	30 years
1894	Billy Hamilton	.521	5 years
1871	LM Levi Meyerle	.500	23 years

The earliest marks here are records only in the sense that nobody had done better yet. Season length, schedule and the rules themselves have all changed, so a figure from the 1870s is not comparable with a modern one and is not offered as though it were.