My vote goes to Chester Arthur. Little was expected of him when he succeeded President Garfield after his assassination in 1881. But he became the best of the Gilded Age presidents. He was scrupulously honest in an era when this was not normative in public officials.
- He infuriated his party by pushing through the first civil service reform (the Pendelton Act).
- He vetoed the Chinese Exclusion Act for being the racist piece of trash that it was (his veto was overridden).
- And he began rebuilding the Navy which had been allowed to largely disintegrate after the Civil War, by constructing modern steam powered warships made of steel and iron. He is quite probably the father of the modern American Navy.