Smedley, I think you've got the date right. I think of the "country music" of today as a commercial product designed by the business world as a more profit-oriented substitute for something natural that people crave, in the same way that Coca-Cola is a substitute for fruit juice, and I think it took that form during the 1950's, concurrent with the rise of "rock music." I think "folk music" in the US sense (i.e. not exclusively or even primarily consisting of traditional songs of unknown origin), is a reaction against that emerging commercialism. Emmylou Harris, asked by an interviewer if she and Gram Parsons think of their music as "progressive country," said that it's actually regressive since they're aiming for the sound that country music used to have.