Steve Gardham wrote: I ought to investigate those songsters when I have time.

FYI, they're all from the Robert Winslow Gordon collection at the Library of Congress, so they're publicly accessible. And a good chunk of the ones I indexed are not in the Roud Index. But they're all from about 1860 to 1870, and most of them are by R. M. de Witt and have a very high degree of overlap. (For instance, de Witt seems to have had only about a dozen pieces of typeset sheet music, and to have dropped the plates of a random eight or so in every book he did, so that he could claim exclusive arrangements.) They won't give you much in the way of earliest dates, and they largely pile up instances of the same song. E.g. the TBI now has more instances of "Little Maggie May," a stupid song about a too-nice girl, than "Maggie May," about a not-too-nice girl, even though the latter is obviously more common in tradition.

https://www.loc.gov/collections/robert-winslow-gordon-songsters/about-this-collection/