To sum up, this song is traditional, dating back probably into the 1930s or before, but has been augmented since 1955 or so with a few songwriter-composed "tin pan valley"-style verses.

As far as I've been able to trace it, the oldest original was sung as early as the 1930s by Bascom Lamar Lunsford, probably learned by him from one of the mountain people he collected his songs from.

It was then picked up by Susan Reed sometime in the 1940s. She may well have learned it from Lunsford personally, perhaps at the Asheville Folk Festival. She then sang it in New York and on the folk circuit in the 1940s and 50s, and made it quite well known.

I think, but am not sure, that the next professional folksinger to spread it around was Bob Gibson. Based on that, the various composers like Fred Hellerman got going on their own proprietary versions, such as the "I'm Just a Country Boy" and "Woody Knows Nothing" variants quoted above.

I've covered this in more detail in the "Woody Knows Nothing" thread:

http://mudcat.org/thread.cfm?threadid=18708#1947471

The two threads ought to be linked to one another, as it's all the same song. Bob