Explorers like Columbus who conquered the indigenous peoples. Slave owners from 1619 to 1865. Statesmen, military leaders and all associated with the Confederacy. All involved in the dispossession and ethnic cleansing of Native-Americans, like Gens. William Sherman and Phil Sheridan who said, “The only good Indian is a dead Indian,” and acted on that maxim.
Lastly, segregationists. There is a move afoot to take the name of Sen. Richard Russell of Georgia, an opponent of civil rights laws, off the Senate Office Building to which it has been affixed for 40 years.
Not really sure Calhoun and Taney are the same as Columbus and Henry Hudson or Washington and James Madison. Or that people who are primarily famous as segregationists really count among "America's Heroes."
I'd keep Russell's name on the office building, since he was a distinguished senator, but I don't think anybody was ever going to propose making his birthday a national holiday.
All this has already happened to the Puritans, though. When was the last time you heard a good word about them (especially from some of the people who are complaining the loudest now)?
Calhoun isn't in the same league of importance as America's founders, but he's a sufficiently significant figure in history to be honored in his native South Carolina. You don't have to agree with his ideology or with the Confederate cause to recognize the Orwellian nature of erasing his memory to make way for multiculturalist icons. As I said, the multiculturalists go after the easy targets (e.g. less universally revered names like Calhoun) first as a dress-rehearsal for erasing the memory of (or the rewriting of) ALL pre-PC US history.
So when someone agitates to change the name of Lake Calhoun to Lake Trayvon Martin, it won't be long until they do the same thing to the Washington monument.