where i found it: the public library
If you want keys to kingdom of old and obscure country music here are two very creatively named good bets: Nick Tosches Country and Charles Wolfe's Classic Country. Dig into the stories of country weirdos such as blind Riley Puckett, minstrel virtuoso Emmett Miller, swingers Milton Brown and his Musical Brownies and the debauched yet soft voiced Lefty Frizzel. Tosches is more gleeful about excess and misery and Wolfe's research is not as good, but you can come away from both of these tomes with a whole new take on what happened to music in the 20th century. Good luck. You might end up listening to nothing but Jimmy Rogers or the Louvin Brothers for a few months.