Google Piedmont Blues and there is some agreement about musicians who represent the style, and then all kinds of opinion and speculation about the origins of the style. The only agreement seems to be that to a greater or lesser extent, there are elements of ragtime piano adapted to the guitar, and the influence of earlier banjo techniques applied to guitar. There is lots of interesting speculation about African and anglo-folk influences, racism, and the transition of the middle south from share-cropping to rural industrial. There is a nod to string band music. What no one mentions is the heady cross-pollination that occurred all along the major rail routes between New York City and New Orleans, that ran through Richmond, Durham, Greensboro and Atlanta. (It was also why the essentially working class, backwater town of Durham has a major history in drug trafficking, dating to at least the late 20's.) In addition, while many African-Americans headed north for better work opportunities aboard the railroad, it tended (and still tends) to be sons and daughters with significant family remaining in the Piedmont, and closely connected extended family with much visiting, traveling, and moving back and forth, adding to the cross-pollination.