I have a [American] Civil War book at home that has a picture of a small guitar from that period (1850's-1860's). [It's not a shoddy book or I wouldn't bother to mention it.]

I know that the banjo, and probably the guitar, were rather popular as "parlor instruments" in the 1890's--sort of past-times for the newly-middle class. Admittedly, the music played on them was of the late-Victorian heavily-sentimental genre and not usually traditional. Possibly they just became more noticeable?

Does anyone know how long the guitar has been in use in Mexico (carried over from Spanish music, I assume)? So much of the western and southwestern US was Mexico until fairly recently (~150 years ago) that the "tradition" of the guitar might be older in those areas than in others.

Hasn't Martin been in business since the first half of the 19th century? I don't know much about the company so they might not have been building guitars the whole time, though.