If you could send me a snail mail request, I could send you, if I can find
one, a copy of the James City report.  James City was set up by the Army
during the Civil War to house "contraband".  We found a couple of privies
from the late 19th cent. on rear lot lines.  You should also contact Nan
Rothchild in New York for the stuff from the Telco Block, Martha Zierden at
Charleston Museum, Charles Cheek at John Milner in Alexandria,  Charles
LeeDecker at Berger in D.C. (he did a paper on them at SHA in KC, as I
recall), etc. etc.  I suspect you won't find much from rural contexts because
they often (perhaps even usually) did not have privies until the late
19th-early 20th.  Even in urban contexts you probably won't find too many
privies except in middle and upper class households until the late nineteenth
century or in very heavily urbanized areas.
 
TomWheaton