Here is one of those rather large questions. Without reading all of the fine print, does somebody already know how many of the "Child" ballads are actually documented by/in Child himself as having been around in the 1800s? In taking a very casual and brief look at Richie's site last night, I kept coming up with dates in the 19th century. If I had a quick and easy list of those ballads that we know were documented in England, Scotland or Ireland in the 1700s, we could at least narrow down the list for what to look for over here in America.
This is not to say that it's not possible for an "earlier" version of a ballad to have survived in the "oral tradition" and gotten over to America before it showed up in print in England, etc. That would be an interesting find!