Lisnaholic, Steve Earle certainly started out in country, I believe Guitar town was his debut. I'm not a huge fan, but I liked his early stuff
He is married to the very good country singer Alison Moorer, who is shelby Lynn's sister
http://www.youtube.com/watch?v=5K2OZUgGqkw
Above is a version of Drug Store truck Driving Man by Joan Baez & some guy
http://www.youtube.com/watch?v=xzBeV7l8bnY
The Byrds
I consider much of the Grateful dead's later work country rock
Here is a great example
YouTube - Grateful Dead - Truckin'