In answer to the query about useful sources on Mark Twain and P. T. Barnum--
I highly recommend Neil Harris's book about Barnum, _Humbug:  The Art of
P. T. Barnum (Chicago:  Chicago UP, 1973).

While it's only about Barnum, Harris does a really good job locating Barnum
in the cultural context of nineteenth-century America.  The book would, at
least, give you some useful background for speculating about connections

between them.

Susan Reed