See the letter from SLC to Bliss, 2 Dec 1867, in Mark Twain's Letters,
2, available online at marktwainproject.org:
"But I know Richardson, & learned from him, some months ago, something
idea of the subscription plan of publishing."
[Note:] Albert Deane Richardson (1833–69), a journalist and western
became chief war correspondent for the New York Tribune in 1860.
Vicksburg while attempting to run past the Confederate batteries with
reporters, he escaped from a Southern prison eighteen months later.
war he compiled two books incorporating his Tribune dispatches: The Secret
Service, the Field, the Dungeon, and the Escape (1865), which had a sale
hundred thousand copies, and Beyond the Mississippi (1867), which sold
seventy-five thousand copies by late 1869. Both books were published and
the American Publishing Company (“Albert D. Richardson,” New York
Dec 69, 1). Clemens’s conversation with Richardson “some months ago”
occurred in January 1867, for on 2 February he said in his letter to the
that “Richardson is hard at work on his new book concerning the Far West,”
published in mid-1867 as Beyond the Mississippi. Richardson’s current
for the American Publishing Company, which would bring him to
Washington, was A
Personal History of Ulysses S. Grant (1868).