If you’re still taking suggestions, I offer: Jim Croce, Harry Chapin, Gordon Lightfoot, and Bobbie Gentry.
Some more possibilities: Tom Rush, Richard and Linda Thompson, Richard Thompson solo, Linda Thompson solo, Van Morrison, Sandy Denny.
And more than a possibility–my dead ringer for this thread and an absolutely stunning artist who needs far more exposure than she has: Eva Cassidy.
For fuck’s sake. I forgot to mention Guy Clark, Townes Van Zandt, Robert Earl Keen, etc.
I recommend picking up a copy of Lyle Lovett’s “Step Inside This House”. It’s a double disc release of Lovett covering songs written by his friends and influences. This one release has turned me onto more exceptional music than any other. Listen to songs, track down original artists, read bios, discover influences and proteges, and pretty soon you’ll have a world of music in the same vein as the OP that just happened to never make the radio.
And Ryan Bingham. I can’t believe I almost forgot him a second time.