“John C. H. Grabill sent one hundred and eighty eight photographs to the Library of Congress between the years 1887 and 1892. This collection is considered the premier collection of western frontier photography in the United States today. Known for their gritty realism, these sepia-toned windows to the past capture the American West in the midst of settlement. The well-crafted images evoke a definite sense of place and time that allow the viewer to peer into a world that otherwise survives only in our imaginations, and the stuff of legends.”

-Margaret McGuire, 2004. From Digital Picture Printing & Framing

Grabill’s photographs are gritty, realistic, and immediate. The entire collection can be found at the Library of Congress. Several sizes are available for download, including hi-res Tiffs.
I used one of his shots of Deadwood, Dakota Terr. to make my banner and another shot of his is my current wallpaper.
Here’s a few of my favorites:

There are many more her and they are wonderful inspiration for your Western game.

The Amon Carter Museum has a web feature called “Texas Bird’s-Eye Views” that features some really nice maps of various Texas towns from 1871-1892. While they are behind a Flash-based map viewer at the website, many of them are also on Wikimedia Commons.

After the Civil War there was an explosion in panoramic or bird’s-eye view city maps. The techniques and technology were sufficiently advanced to produce beautiful works of art. There is a detailed article on Bird’s Eye View map phenomenon at the Anon Carter site.

Below are some samples:
Austin, 1873.
Austin, 1887.
Eagle Pass, 1887.
Fort Worth, 1876.
Fort Worth, 1886.
Fort Worth, 1891.
McKinney, 1876.

All told there are 60 maps on the Amon Carter site, and many are also available on Wikimedia Commons and these are only for Texas towns. I’m sure with some digging we can find more primary source maps of Old West towns, in fact you can count on it.