Query: When was the first American edition of On the Origin of Species published?
Context: Darwin was delighted by the popularity of the book, and asked Gray to keep any profits. Gray managed to negotiate a 5% royalty with Appleton's of New York, who got their edition out in mid January 1860, and the other two withdrew. In a May letter, Darwin mentioned a print run of 2,500 copies, but it is not clear if this referred to the first printing only as there were four that year.