The issue was addressed and hotly debated when drafting the Constitution.
On enumeration: Apportionment for Representatives and taxation purposes would be determined by the number of free persons and three-fifths "of all other Persons" (Art. I, Sec. 2). The pro-slavery delegates wanted their slaves counted as whole persons, thereby according their states more representation in Congress. It was the anti-slavery delegates who wanted to count slaves as less-not to dehumanize them but to penalize slaveholders. Indeed, it was antislavery delegate James Wilson of Pennsylvania who proposed the three-fifths compromise. Also, this clause did not include blacks generally, as free blacks were understood to be free persons.
On the slave trade: Congress was prohibited until 1808 from blocking the migration and importation "of such Persons as any of the states now existing shall think proper to admit" (Art. I, Sec. 9). Although protection of the slave trade was a major concession demanded by pro-slavery delegates, the final clause was only a temporary exemption from a recognized federal power for the existing states. Moreover, it did not prevent states from restricting or outlawing the slave trade, which many had already done. "If there was no other lovely feature in the Constitution but this one," James Wilson observed, "it would diffuse a beauty over its whole countenance. Yet the lapse of a few years, and Congress will have power to exterminate slavery from within our borders." Congress passed such a national prohibition effective January 1, 1808, and President Jefferson signed it into law.
On fugitive slaves: The Privileges and Immunities Clause (Art. IV, Sec. 2) guaranteed the return upon claim of any "Person held to Service or Labour" in one state who had escaped to another state. At the last minute, the phrase "Person legally held to Service or Labour in one state" was amended to read "Person held to Service or Labour in one state, under the Laws thereof." This revision emphasized that slaves were held according to the laws of individual states and, as the historian Don Fehrenbacher has noted, "made it impossible to infer from the passage that the Constitution itself legally sanctioned slavery." Indeed, none of these clauses recognized slavery as having any legitimacy from the point of view of federal law.
Beiruty wrote:For historical perspective:
So from 1776 to 1861, slavery was legal in the USA. That is 85 yrs of legal ownership of slaves. What did the constitution mention about slavery?
Why the issue was not addressed for so long? Did the northern states have slaves?