Virginia, the largest slave state (also had more free blacks than any non-slave state) seriously considered emancipating slaves in the 1830s. The effort was led by Thomas Jefferson Randolph.
The discussion on slavery in 1831-32 were, in part, due to the Nat Turner rebellion. The idea of gradual emancipation fell apart on how to accomplish it and what to do with all the freed blacks once it was done. Those advocating emacipation also linked it with forced colonization, which was what Mr. Randolph's illustrious ancestor advocated a decade or so before. Eventually the emancipation plans were shelved, but the forced removal part was later added to Virginia's constitution during the 1850-51 constitutional convention.