Guest:
If you research many of the songs, and try to find the roots of the song and melody, you will find the evidence. You may also look in the music collected from Appalachia, the Smokey Mountains, and along the Shenandoah. The trail is there for much of the pre-Civil War music also. Just take the time. It is interesting. I have been collecting this music for over 50 years. By the way, have you ever traced the song Streets of Laredo back to its origins? It, too, has Civil War versions, but it apparently originated in England sometime in the 1600s as The Unfortunate Rake.
Gordo