Truman (HST) assumed the presidency in the Spring when I was in the 6th grade. He left office in the winter of my sophomore year of college. I learned a lot from him. For example, he said that one couldn't get rich in politics if you were honest. I think of that often, when observing current politicians who did not start off wealthy, but became so during or after serving in office, parlaying political influence into money: Newt Gingrich, Rick Santorum.
HST pushed for universal, compulsory health insurance, which caused the Republican party to have a collective seizure. My classes were visited by local dentists and MD's to instruct us in the evils of such a system, and to convince our innocent minds of the great dangers in 'creeping socialism.' (It didn't work; I wound up a right-wing socialist.)
He once proposed in a speech that higher executive pay should be capped at a certain percentage of the workers' pay in the company. This really set off a storm among conservative republicans. (I grew up in an extremely right-wing, although libertarian, part of the country.)
One of my favorite comments of his, since my family was poor, was about democracy. He pointed out that if we really believed in democracy and equal opportunity that we would
support an estate tax of 100%. In that case, everyone would start off on the same footing. Surprisingly, in those days, this caused less of a storm than his other proposals.
As far as I can tell, there is now a consensus among historians that HST is one of the great ones. There is also somewhat of a consensus that, in order to be a great president, one must have a strong knowledge of history, as Truman did. Jefferson, Lincoln, Theodore Roosevelt, John Kennedy and Truman all had an excellent knowledge of history, mostly self-taught. Franklin Roosevelt was also a great president, so busy making history that I never caught on to how much past history he knew.
Most of the people around me never bought any of this; my father went to his grave believing HST to have been on one of the worst presidents. But even he, if he were judging the current crop of republicans, would be impressed by how poorly they stack up to a president who really believed in democracy, fairness, knowledge of history and honesty. The current republican party has clearly lost its bearings, completely.