I am writing a play set in the period & places above.

Please suggest some on-line sources that will help me to adapt the
dialogue accordingly.

probonopublico,

Very interesting question and I thank you for the opportunity to
answer it.  Here are some resources that I think will be of
assistance:

A 19th Century Slang Dictionary
http://www.marchforpreservation.com/a_19th_century_slang_dictionary.htm
A very nice collection of 19th century slang and terms.  The great
thing about this source is that it gives literary citation to where
the terms were actually used.  Several are from the mid- to late 19th
century, however I am sure you can find some useful terms.

Did You Know?
http://www.lib.ucdavis.edu/exhibits/food/panl6ukno.html
Has a few slang terms used in the American West in the late 1800's. 
Not alot and pretty specific, but may help

Old West Slang
http://ladybelleoutlaw.homestead.com/OldWestSlang.html
Nice collection of terms used in the Old West

I realize your question asked for online sources, however, there are
some print references you may want to check as well:
"English Slang in the Nineteenth Century".  
http://www.amazon.com/exec/obidos/ASIN/1855069520

"Slang Through the Ages" 
http://www.amazon.com/exec/obidos/ASIN/0844208345

Random House Historical Dictionary of American Slang: A-G (Vol 1)
and
Random House Historical Dictionary of American Slang, H-O (Vol 2)
http://www.amazon.com/exec/obidos/tg/detail/-/067943464X/qid=1044210470/br=1-14/ref=br_lf_b_14//103-0808476-0939818?v=glance&s=books&n=11619

Thanks again for your question.  If you need additional clarification,
please let me know prior to rating my answer.

Regards,

-THV

Search Strategy:
19th century colloquialisms
19th century colloquialisms american
19th century colloquialisms england
19th century slang

Hi, thv

Many thanks for your brilliant research.

They are just what I require.

Kindest regards

Bryan

Bryan..

Thanks for the 5-star rating and your generous tip!  Good luck with
your play and I am glad I could be of assistance!

-THV

The standard contemporary reference work, the one on which all
subsequent references are based, is:


SLANG AND ITS ANALOGUES, Farmer, J.S., Henley, W.H., Arno, NY, 1970,
one volume reprint of the original 7 volumes, 1890-1904 (Distributed
by Crown).


hlabadie-ga

Many thanks, hla...

I have taken note!

Kindest regards

Bryan