Steve, I agree with your assessment of this. However, I am still hoping that along the way we might turn up further documentation for that probability. In the "Barbara Allen" example from Northern Pennsylvania, there is no way to say for sure that it was known there in the 1700s, but we can document the fact that the singer was born in 1777. Thus, there is the possibility that he learned it as a young person growing up. It's also possible that it didn't show up in his life or his region until later on in his life. I was just glad to get a 1700s date associated with one of the ballads over here.
Your example in the second posting in this thread up above about:" 'A Pioneer Songster' edited by Harold W. Thompson.... an anthology of ballads from the Stevens-Douglass Ms of Western New York, 1841-56" is another example of some real possibilities. If those songs were being sung by adults, especially older adults, in 1841, there is a very good possibility that they may go back into the 1700s. I see some parallels between the Western New York collection and this collection from Northern Pennsylvania. They are geographically quite close to each other, which further supports the idea that this was a region in which these songs were and perhaps had been popular for some time.