Only U.S. Monument to a War Criminal
Henry A. Wirz was the officer in charge of the Confederate prison at Andersonville. Nearly 14,000 Union prisoners died during his relatively brief tenure, so he was tried as a war criminal and hanged in Washington, DC, on November 10, 1865.
Some people in the South felt that Wirz got a raw deal. In 1908 the United Daughters of the Confederacy erected a monument honoring Wirz in the center of Andersonville, "to rescue his name from the stigma attached to it by embittered prejudice." The monument blames the Union deaths on "the harsh circumstances of the times and the policy of the foe," and claims that Wirz was "the victim of misdirected popular clamor," and that he "indignantly spurned a pardon, proffered on condition that he would incriminate President Davis." That's Jefferson Davis, president not of the United States but of the perfidious Confederacy.
Maybe Wirz's lasting punishment is that the people on his side went to all the trouble of erecting a big monument, filled it with inscriptions in his defense, but didn't make it particularly interesting to look at.