I think Piedmont blues is a relatively new style. According to Wikipedia, it derived from the earlier guitar and banjo styles of frailing or framming, ragtime, and parlour guitar styles.

Another article (links below to both Wikipedia and the UNC Ashville article), Piedmont Blues in some ways has more influence from "White" music than does Delta blues, but is also reflects West African roots.

http://en.wikipedia.org/wiki/Piedmont_blues
http://facstaff.unca.edu/sinclair/piedmontblues/Default.htm

According to Mike Seeger, the guitar was a relatively late comer to the South in terms of being widely played. His album presenting Southern guitar styles starts with about 1850.

Don't forget how the railroad spread musical influences either. The rail line from New York to New Orleans carried blues and jazz musicians up and down through Maryland, DC, Virginia, across the North Carolina Piedmont through Raleigh, Durham, Greensboro, Charlotte, then on through Atlanta and Western Georgia on a regular music and performance circuit. All kinds of cross-pollination of music occurred along the way (not to mention a thriving drug trade in cocaine and heroin dating back to the late 20's and early 30's.)

Janie