You might want to look at Ham Hill's MARK TWAIN AND ELISHA BLISS and my own
articles on Twain that appeared in FIRSTS MAGAZINE in 1998, for insights
into the publishing practices of the American Publishing Company. There are
also some good studies of subscription publishing in the late 19th century,
but not all of that info would apply to APC, or to Twain's books published
by APC.

The books were printed in Hartford (sometimes a book would have sheets
printed at more than one press, and from more than one set of plates). The
books were then shipped to the major cities where APC had regional
distributors. The largest ones appear as co-publishers in some imprints (see
my article on THE GILDED AGE for a long list of imprints). On some of
Twain's books APC used number codes on the bindings instead, or stamps on
the endpapers. But to answer your primary question, the books were printed
and bound in Hartford, and then shipped. Keep in mind a publisher could keep
sets of sheets warehoused and print up the front matter (with the title-page
and multiple imprints) as it was needed --a common practice. But in the case
of a single copy of THE GILDED AGE, I have a copy with a cancel title-page
in a sheep binding. I suppose the publisher got an order for a sheep copy
(or copies) from Bancroft and rather than grab some sheets and front matter
and then bind them up in sheep (which was a costly binding that was not
warehoused in large numbers), they just took whatever sheep copies they
already had in stock and canceled the title-pages and sent them along. The
title-page was from APC type fonts, not printed in California.

In California it was commonplace for Bancroft (the San Francisco
co-publisher) to cancel ad leaves that contained prices, since California
prices had to be somewhat higher to recover the higher shipping costs. Not
just books, but prospectuses sent to California often had price information
removed and replaced with a locally printed cancel leaf with higher prices.
Regardless of where you lived, you could become a door-to-door agent by
writing directly to Hartford. But regional distributors (aka co-publishers)
also sent out flyers to attract door-to-door agents. I have examples of such
flyers and prospectuses in my personal collection.

For accounts of what it was like to be a subscription book agent, see FACTS
BY A WOMAN (the authoress sold Tom Sawyer in California), and DIARY OF A
BOOK AGENT (the author unwittingly knocked on Mr. Samuel Clemens door in
Hartford and tried to sell Mr. Clemens a set of Mark Twain's works --without
knowing who he was-- which inspired Twain (or was it Clemens?) to order a
set for a friend as a joke).

Kevin Mac Donnell
Austin TX