With regard to pre-CivilWar concertinas in the US, the aforementioned piece in Concertina & Squeezebox also states:

"We read in issue #16 of our Australian sister publication, 'Concertina' that the English concertina at least , seems to have arrived here (on) November 25th, 1847 in New York City brought by English pianist Richard Hoffman. The poster for that concert announces he will 'introduce' the concertina to the American public for the first time, playing the Fantasia on Themes from the opera 'Norma.'"

Referring to the American Musical Dictionary of 1861, the article also cites the existance of one concertina teacher, William H. Currie, at W. 28th St., and one accordian teacher, Charles Rosenberger, E. 13th St., both in New York City.

Ubcommon or unusual, but nevertheless here at that time.

Keep on squeezin' -- Tom