I'm afraid I had to read FRiend Lee's post a couple of times before it got through my thick skull that she meant going back in time to George Washington, not Abraham Lincoln returning to Washington. D.C.
Mary Todd Lincoln's family, the Todds, were prominent in Kentucky and slave holders. I never heard anything about Lincoln personally owning slaves, so I can't comment; maybe that goes along with the rumor that he was gay because he shared a bed with his law partner when he was a young lawyer. Anyway, Mary Todd Lincoln had relatives--I think a brother or brothers (I didn't check)--who fought for the Confederacy. (I really don't understand how that marriage came about. Considering her family's prominence, Mary Todd was definitely marrying "beneath herself" when she married Lincoln. Maybe her family already suspected that she had emotional problems and thought it best to marry her off to an unknown lawyer from Illinois, where she and her problems might be inconspicuous.)
George Washington definitely owned slaves before he managed to marry Martha Dandridge Custis, who, I guess by the standards of Virginia at that time, was a stinking rich widow.
(Jefferson wrote those words in the Declaration of Independence. James Madison wrote the Constitution. Of course, Jefferson was referring to free White male property owners over the age of 21.)