On the specific issue of slavery, as our editorial noted, Jefferson did quite a lot of good, and not only because of the pivotal role played by his “all men are created equal” rhetoric in inspiring later generations. He was a lifelong opponent of the transatlantic slave trade, perhaps the nation’s most vocal, consistent, and ultimately successful opponent. In 1776, Jefferson tried to get a denunciation of the trade into the Declaration of Independence. In 1778, as governor of Virginia, he signed into law a state ban on importing slaves (a bill he may or may not have authored). The Constitution forbade the federal government from banning the slave trade before 1808; as president, Jefferson called on Congress in his 1806 State of the Union message to ban it at the first moment allowed by the Constitution and “withdraw the citizens of the United States from all further participation in those violations of human rights, which have been so long continued on the unoﬀending Inhabitants of Africa, & which the morality, the reputation, & the best interests of our country have long been eager to proscribe.” He signed that ban into law in 1807. True, the ban on the external slave trade was in the financial interests of Jefferson and other Virginia planters, who could sell their slaves internally to the Deep South — as with so many things, the issue had its trade-offs and moral complexities — but the fight against the transatlantic slave trade was the central battlefield of the abolitionist movement during Jefferson’s political career, he was on the right side of it, and he succeeded in ending America’s involvement in it.
Jefferson’s record on the domestic expansion of slavery was mixed but also had genuine and enduring positive influences. In 1784, Jefferson proposed to the Continental Congress a ban on slavery in all the territory west of the Appalachians after 1800. His bill, the Territorial Governance Act, failed by one vote, but Jefferson’s language was included in the final, narrower Northwest Ordinance passed in 1787, which banned slavery west of the Appalachians and north of the Ohio River. The Northwest Ordinance helped create the free states of the Midwest that proved decisive in the long-term free–slave state balance. Moreover, the language Jefferson used in 1784 was reused by Congress in 1865 for the 13th Amendment. Thus, Jefferson is, literally, the author of our constitutional ban on slavery.