John Montgomery Ward for the Providence Grays.
Interesting note: Monte won 164 games in his major league career before he turned 25. However, he was converted into a full-time position player when he was 24, and despite playing till he was 34, never pitched again.
He was also instrumental in creating the player's league.
"I do not think baseball of today is any better than it was 30 years ago... I still think Radbourne is the greatest of the pitchers." John Sullivan 1914-Old athletes never change.