Oh, Ta-Nehisi Coates is gonna like this...guess which president's stock has improved the most since the last Siena College survey? That's right, it's Ulysses S. Grant.
Grant was close to the bottom in the first three Siena polls (1982, 1990, 1994), beating out just three presidents each time. In the 2002 edition, he moved up the 35th (of 42). Now, he's escaped the ranks of the failed presidents entirely, rising to a respectable 26th. This matches what other surveys have been showing. The very first such study, conducted in 1948 by Arthur Schlesinger, Sr., had Grant second-to-last, and up until recently he was invariably a bottom-five choice. Now, with Siena joining the crowd, he's a mid-pack president. Siena's respondents docked him for his executive appointments and executive ability, and didn't really give him strong marks anywhere, with it all averaging out to 26th place.
I have to admit that I probably know more about the historiography here than about the actual history of the Grant presidency. The historiography is straightforward: Southern-dominated history cast Grant as the scapegoat for pretty much everything. Grant was uncouth and brutal while Lee was civilized and tragic. Grant spent eight years drunk while crooks raided the treasury and crazies took revenge on the South. Something like that. Lincoln was sainted -- that almost couldn't be helped -- but his death left the presidency in the hands of buffoons who allowed the greedy carpetbaggers and clown-like (at best) ex-slaves to punish the South even more over that tariff-dispute thing that tragically divided honorable Americans.
Of course, that was all nonsense, and it's finally starting to recede, and with that Grant's ratings are improving. I have only the vaguest of notions, however, about where he really should be in this sort of ranking. My geuss is that I'd probably wind up putting him somewhat higher, somewhere in the broad range of 13th-22nd, if I was doing a ranking right now, but I'd be stabbing at it..
The obvious recommendations for Grant are his memoirs, which I haven't read, and TNC"s recent series of posts as he was reading the memoirs, which I have (links to the last one, I'm not aware of any index, alas). But really, since what interests me in this post is the historiography, there's only one place to send you: you really have to watch Birth of a Nation. It's all you think it is...you just have to watch it, and understand that it was White House-sanctioned history, of a piece with most grade school and high school American history texts, and not the ravings of some loony remnant faction.