The reason for including this clause was explained by Richard Dobbs Spaight, who had served in the Confederation Congress, in the North Carolina House of Commons, and as a delegate to the Constitutional Convention. Some delegates from the northern states wanted to abolish the slave trade completely and immediately, whereas some delegates from the southern states didn’t want the federal government to interfere in the slave trade at all. Slave labor was essential to the southern economy, so those delegates “would not consent to the desire of the Northern States to exclude the importation of slaves absolutely.”

A compromise was reached. It was agreed that the slave trade would operate unmolested for twenty years, and it was generally understood that the trade would be outlawed in 1808 (which it was). Southern delegates agreed to this compromise because (quoting Spaight) “they were now in want of hands to cultivate their lands,” but “in the course of twenty years they would be fully supplied.” Some delegates in southern ratifying conventions claimed this compromise as a victory for the slave states, because it officially protected and sanctioned slavery on the federal level, if only for a limited period of time.

Antislavery champions of the Constitution had a more difficult time rationalizing the twenty‐​year clause. How could they agree to sanction a practice that they personally regarded as cruel and murderous? How could they boast that the new Constitution was intended to “establish Justice…and Secure the Blessings of Liberty” when it told potential kidnappers and murderers that the federal government would not interfere in their activities for twenty years?

One path was to claim that the twenty‐​year clause was actually a step toward the abolition of slavery. Edmund Randolph, the governor of Virginia who played an important role in the Constitutional Convention, flatly denied this rumor during the Virginia Convention (June 21, 1788). Even South Carolina, Randolph told his follow Virginians, believed the clause provided security for slavery.