"In 1779, as a practical solution, Jefferson supported gradual emancipation, training, and colonization of African-American slaves rather than immediate manumission, believing that releasing unprepared persons with no place to go and no means to support themselves would only bring them misfortune. In 1784, Jefferson proposed a federal law banning slavery in the New Territories of the North and South after 1800, which failed to pass Congress by one vote." he didn't set his slaves free all at once, but he did. https://en.wikipedia.org/wiki/Thomas_Jefferson_and_slavery.