How many US Presidents were slave owners?

I wouls say, without being absolutely certain, that the list would include Washington, Jefferson, Madison, Monroe, possibly Andy Jackson, William Henry Harrison (maybe), John Tyler (maybe), James Polk, Zachary Taylor and, Andrew Johnson may possibly have been a slave-holder before the civil war--but i don't know it for a fact. I've largely based this on the states of origin of the presidents, although i'm certain of the first four.

Washington, Jefferson, Madison, Monroe, Jackson, Van Buren, WH Harrison, Tyler, Polk, Taylor, A. Johnson, Grant

It's important then also, to remember which ones were good to their slaves and set them free when they died. It's hard to place blame in simply owning slaves, as that was the time, but we should examine which ones found something wrong with it and were not abusive.

Jefferson found something wrong with it, and said so, and he was not abusive. He did little to nothing for his slaves, however. Washington had inherited, in the terms of the day, the responsibility for the slaves which Martha Dandridge Custis brought to their marriage by proxy--the slaves and lands were in trust for her children by Daniel Parke Custis. Washington finally quit the Virginia militia in disgust or exhaustion or both before the end of the French and Indian War, and it was thereafter that he married Martha. He devoted his not inconsiderable energies and penetrating eye for detail to the management of the estates at Mt. Vernon which he had gotten from his half-brother Lawrence. He immediately saw that tobacco culture was ruining the soil, that the London tobacco factors were robbing the planters blind and keeping them in constant debt, and that slave labor was inefficient in the best of circumstances. By the time the Stamp Act crisis and the "boycotting" (actually an anachronism for 1765) of English goods came along, he was already heavily into diversified agriculture and productive self-reliance.

He was haunted by the idea that his death before that of Martha would leave her in a position of being a potential murder victim if the slaves anticipated their manumission upon her death. So he set up a pension system for the slaves. He had employed the ones who were skillful and willing to work, teaching them trades and paying them. For the rest of his labor, he relied upon hired labor. The financial strain on his estate was enormous, but he also had enormous land claims from his days as a teenaged survey for the county. I believe i am correct in stating that his estate continued to pay pensions to his and Martha's former slaves until the 1830's. Sadly, his non-descendant heritor, George Washington Parke Custis, did not have the same scruples.