I Ran across a cd at my library called"East Virginia Blues".
It's one in a series of 11 called "When The Sun Goes Down,The Secret History Of Rock & Roll".
Don't let the term "Rock & Roll"throw you.
The cd I'm listening to has got 25 tracks of some great "clean" recordings of artists like the Monroe Bros,Wade Mainer,Rouse Bros,Blue Sky Boys,Cliff Carlisle,Etc.
I Haven't had time to check out the rest of the series in depth, but what I've seen looks promising,especially some of the recordings attributed to early blues.
Some here probably know about this already,but I thought it worth sharing.
Here's the link;

http://www.bluebirdjazz.com/whenthesungoesdown/index.html

DB.