As far as I've heard, the earliest banjo tutor is Gumbo Chaff's, and specifically the 1848 edition referred to by Gura and Bollman in America's Instrument, p. 266, note 55. I've discussed (on that other Gumbo Chaff thread) an 1843 "accordeon" preceptor I have, that contains a few "Ethiopian" tunes. But I just noticed, I also have a violin book by Elias Howe that's dated 1847. This was the last year before he started publishing specifically for the banjo; specifically "Ethiopian" collections; and titles under the pen name "Gumbo Chaff" (all of which, I believe, refer on the title page to some minstrel company -- usually Christy's).
The back cover of this book lists a lot of publications he already had available in 1847; the front cover mentions Ethiopian Melodies; and the Index lists a few minstrel show tunes (they hover around p. 27). So I thought I'd post those pages as a sample -- "Gumbo Chaff's bookshelf, 1847."
Dick