Written by Tom Campbell and Steve Gillette, and first recorded by Ian and Sylvia on their Early Morning Rain album, Vanguard 79175, 1965.
From the liner notes: Written for Ian and Sylvia by two friends in California, one of whom, Sylvia says, had considerable experience as a student of an eminent folklorist where much effort was given to writing songs that would fool the teacher and pass as authentic. Ian feels this is no less authentic, for it was written in the tradition of oldtime cowboy tunes -- just sentimental enough. And mighty convincing in its mention of names and places.
I have seen similar comments about its origins in print elsewhere. It is one of those songs that I never tire of hearing, even after more than 30 years.