If there are shared roots for both folk & country, as people are suggesting, when did the big divide really kick in - is it with the 'commercialisation' (I have reservations about that word but you'll know what I mean by it) of country ? Which would, and excuse me if my U.S. history is a bit askew, pretty much coincide with the strong linkage between folk in the US & Civil Rights. So it's a divide that gets seriously entrenched around the late 50s / early 60s.