McGwire homered off 65 pitchers in 1998. 60 Home Runs pitcher counts.

Mark McGwire homered off an astonishing 65 pitchers in 1998 when he set the season home run record with 70. Barry Bonds and Sammy Sosa homered off the second highest number of pitchers: 58.

Babe Ruth homered off by far the fewest: 33. Even in 1921 when Ruth hit 59 home runs he homered off more: 37.

Here's the box score:

	Year	HR	Pit	4	3	2	1
Bonds	2001	73	58		3	9	46
McGwire	1998	70	65			5	60
McGwire	1999	65	56	1		6	49
Sosa	1998	66	58		2	4	52
Sosa	2001	64	46		4	10	32
Sosa	1999	63	52		1	9	42
Maris	1961	61	46		3	9	34
Ruth	1927	60	33	2	7	7	17
Ruth	1921	59	37		4	14	19

The numbers across the top are the number of pitchers. Ruth and McGwire are the only ones to homer off pitchers four times in one of those seasons. McGwire off Andy Ashby. Ruth did it to two pitchers:
Milt Gaston
Rube Walberg.

Bonds homered three times in 2001 off these three pitchers:
Jason Middlebrook
Curt Schilling
Chan Ho Park.

Maris homered three times in 1961 off these three pitchers:
Jim Perry
Frank Lary
Pete Burnside

Finally, the 7 pitchers who each gave up three home runs to Babe Ruth in 1927:
Slim Harriss
Ken Holloway
Joe Shaute
Tommy Thomas
Sloppy Thurston
Tony Welzer
Tom Zachary: 22,36,60.