The fortunes that were made as a result of the slave trade were primarily in Boston and New England. The trade triangle went like this: New England fisheries, codfish in particular was traded as a cheap source of protein to feed slaves in the Caribbean sugar cane plantations for sugar. Caribbean cane sugar became rum. Rum was traded for more slave. A profit to the ship owners was made at each leg of the trade triangle. Yes, Southerners bought the imported slaves (as did some Northerners), but it was the agriculture of the mid-atlantic and southern states that ran on slave labor -- indigo, tobacco, cotton, corn.
So, the Southern slave owners had their share of guilt to be sure. But most of the "Old Wealth" of New England and in particular, Boston, came from the shipping trade, particularly the trade of slaves, rum, and codfish.
And to be sure, there were European and African slave traders who profited, as well. Year after America abolished slavery and fought a Civil War to, in part, end slavery, there was still a flourishing slave trade between Europe, Africa and South America.
So those of you history buffs who blame the "South" for the evils of slavery, take the mote out of your own eye. There was a huge amount of money made on the slave trade by New Englanders, and the "Peculiar Institution" and the profits made from slavery were certainly not confined to the Southern United States, to be sure. But again, that's history, right? And we all know this, right? And after all, Lincoln's Emancipation Proclamation freed the slaves -- historical footnote -- freed the slaves only in the states south of the Mason-Dixon line, not north of it. And when Lee surrendered to Grant, I believe Grant was still a slave holder, while Lee had freed all of his slaves at the start of the Civil war.
Want to read about the history and economics of slavery? Check out Thomas Sowell's several books on the subject.
Another historical footnote: America's greatest Calvary Officer of all time, Nathan Bedford Forrest was a notorious slave trader. Indeed -- he specialized in buying slave families that would have otherwise been split and sold piecemeal and finding slave buyers who would agree to keep the families together. Does that excuse slavery -- no.