I can't post this in the 'Authors' Resource Centre,' so a moderator can move it, if deemed it should go there. Thought this list will save others a lot of time researching appropriate books for western facts.
Here are some of the reference books I use for western historical fiction.
A dictionary of the Old West, Watts
Brothels, Bordellos, & Bad Girls, MacKell
Curley's Guide to the Black Hills, Curley 1877
Daughters of Joy, Sisters of Misery, Prostitutes in the American West 1865-90 Butler, Anne M.
Deadwood, Parker
Gold in the Black Hills, Parker
Gold Rushes and Mining Camps of the Early American West, Fisher, Vardis
Gold, Gals, Guns, Guts, Lee/Lindstrom
Hard Knocks-A life Story of the Vanishing West, Young
How to Write the Western Novel, Braun (good bibliography)
I Buried Hickok, Secrest
Old Deadwood Days, Bennett, Estelline
Pioneer Days in the Black Hills, McClintock
Saloons of the Old West, Erdoes
Soiled Doves, Prostitution in the Early West, Schissel
Standard Catalog of Fire Arms, The Collector's Price & Reference Guide, Shideler
The Black Hills, or Last Hunting Grounds of the Dakotahs, Tallent
The Old West, The Gunfighters, Trachman
The Prairie Traveler, Marcy
The Real Deadwood, Ames
The World Encyclopedia of Pistols Revolvers and Submachine Guns, Fowler, North, Stronge
The Writer's Guide to Everyday Life in the 1800's, McCutcheon
The Writer's Guide to Everyday Life in the Wild West, Moulton
Upstairs Girls, Prostitution in the American West, Rutter
Western Words, Adams
Wild Bill Hickok, Turner
Women's Diaries of the Westward Journey, Schlissel