one of the interesting things we learned on a tourist visit to a SC historical plantation last winter was that there were educated black slaves who were entrusted to handle money and business for the plantation. it wasn't that they were free, they carried official permits from the plantation owner allowing them to travel and conduct business. after the civil war, that system was abolished, and they became employees.
bottom line: not all slaves were created equal. some of em were field niggers, and others worked in the house. and there was an overseer class, also niggers, who brandished whips and guns and shit, and kept the field niggers in line ...