I'm kind of getting frustrated with the songfile site. It doesn't tell copyright dates, which would help a lot in picking which song with the same name it might be. Then I looked for "Done Laid Around," which the source was attributed "Trad. Arr. Rowan" (actually several of the attributions including Pentangle's mentioned "Trad." but I'm guessing that was their best guess at the time). If you select that song, it sounds like the royalties would go to Peter Rowan, and I'm pretty sure he just did an arrangement of it.
Anyway, for really finding out copyright info, I think the US Gov site:
http://www.copyright.gov/records/index.html
is better. But I looked for "In the Valley of the Shenandoah" and nothing came up in the search. Which might be an argument it's P.D.
There, I'm back on topic.
Brad Sondahl