Steve, Norm Cohen's 2005 article, "The Forget-Me-Not Songsters and their Role in the American Folksong Tradition" (American Music, XXII, 137-219) attempts to disentangle and date the various booklets carrying that title. Their contents differ considerably.

Cohen believes the earliest edition was published by Robert H. Elton in New York in 1840-41. Earlier dates, which are occasionally proffered, seem to be based on wishful thinking only.

If you can't access the article through JSTOR, email me and I'll see if I can find a way to get it to you.