The "brown people" of Appalachia have been in song and story for almost four centuries now, and the unique culture that grew out of these folk (actually consisting of quite a few different strains) constitutes the "bluegrass" heritage.
And yet, they seem to be getting rediscovered all the time. When the Tennessee Valley Authority was plotting out land in the 1930's to build power dams in Tennessee and Kentucky, they kept discovering pockets of these people who still spoke an Elizabethan English and were almost totally illiterate.
I was in the Greenville/Spartanburg area of SC and would have sworn the waitresses were Brits -- but they weren't......
I remember reading about them in the Tennessee Blue Book in school. Of course that was in the 50's when we actually studied history.