This is an interview but is very interesting. There is links to the original article that ran in August in southern newspapers. Also the comments are unusually good and well informed that is also well worth a glance.
Frank Hyman: Yeah, but most of the profit then, as now, went to the one-percenters – people at the top of the pile. About a third of Southern families did own slaves, so it was pretty widespread, but there were plenty of families that might own one or two enslaved Africans. They weren’t wealthy. The bulk of all slaves were owned by the top 5 percent or 10 percent of Southern families.
A small number of people in the South profited immensely. In my research I found that most of the one-percenters in the US were Southerners, not Northern industrialists. The Southern states were wealthier than any nation in Europe except for England, because there was so much money to be made growing cash-crops if you weren’t actually paying people to help you harvest them.