And he was very much his own man, even more so when he became President. Against a lot of opposition, he integrated the military (which I believe had been segregated by Wilson) and supported the creation of the State of Israel, against the opposition of George Marshall.
As you said, I do believe that he grew into the office as a great President, but all the "raw materials" were there before he ever got into politics. If you ever get a chance, a terrific biography was a made for TV movie, starring Gary Sinese.
When I was little, I remember Truman mowing his own yard in Independence.
Mark
What hit me is that I understand he was the last president to leave office and not get a pension.