Just remember the NE also had slaves until it was no longer profitable to do so.I posted that as a response to whether equality was granted by the Constitution. It wasn't explicitly until those amendments. But that doesn't mean that all of the founders were in favor of slavery. Many from the Northern states were in favor of abolishing slavery in the original Constitution. For example, "In denouncing a clause that preserved the slave trade until 1808, Constitutional Convention delegate Luther Martin chastised the institution as "inconsistent with the principles of the Revolution, and dishonorable to the American character." (Slavery and the Constitution | National Review)
Unfortunately, louder voices prevailed at that time. But a major historical point that's often missed is that while chattel slavery had existed under the British for nearly 170 years at that point, and worldwide for thousands of years, it was completely abolished in this country within only 80 years, a single lifetime, of the formation of our Constitution!