|A Slave Ship|
Even though the North did not have a large number of slaves, they were the ones that owned and manned the ships that carried on the slave trade. Thomas Jefferson wrote this about the debate over the Declaration of Independence:
The clause too, reprobating the enslaving [of] the inhabitants of Africa, was struck out in complaisance to South Carolina and Georgia, who had never attempted to restrain the importation of slaves, and who on the contrary still wished to continue it. Our northern brethren also I believe felt a little tender under those censures; for tho' their people have very few slaves themselves yet they had been pretty considerable carriers of them to others.1By 1808 several more states had outlawed the slave trade and Congress outlawed it on January 1st, the earliest date that it was permitted to by the Constitution. When the Southern States left the Union and formed the Confederacy, not only did they not try to reestablish the slave trade, it was actually outlawed in the Confederate Constitution. They did not want to be associated with what they considered the evil practice of the slave trade.
1. Autobiography of Thomas Jefferson, p. 16-17. Source.