Out West, early on, it was lawless and rugged and full of guys who wanted land, gold, and water rights, and sometimes did not get along with the Native Americans who came first. So Out West is also where forts and the United States Army Cavalry could be found. Maybe your ancestor lived near a fort, or maybe he lived in one as a soldier.

Walters Art Museum {{Commons:File:Alfred Jacob Miller – Fort Laramie – Walters 37194049.jpg}} at Wikimedia Commons
You will probably be surprised to know how many forts actually existed in the 19th century Out West. I don’t have an exact number, but I have some resources that will help you track them down, and also find the records created by the U.S. Army at those forts.
First, which forts existed in the states you are researching? I point you, once again, to the Research Wiki at FamilySearch. In the search box, simply type “Wyoming military records”, or whichever state you are interested in. You will get a nice list of forts, along with links to more information or records:

These are mostly links to Wikipedia articles, or websites devoted to particular forts. For the actual records created by the U.S. Army at these forts, check out National Archives Record Group (RG) 393 titled, “U.S. Army Continental Commands, 1821-1920.” You will not find these records at the Family History Library or likely any other library. They are at the National Archives or one of the Regional Branches of the NARA. Yes, this is hardcore genealogy, but you can do it! Refer to my original post on accessing record groups on the National Archives website for detailed instructions on finding this record group and getting your hands on the records. Under heading 393.7 Records of Posts here is a glimpse of what you will find:

Is it just me, or does everyone else get excited about finding “Letters received, with indexes and registers; endorsements; telegrams; issuances; registers; reports’and other records…”? No, see, you are a genealogy geek, too, and your pulse just elevated a tiny bit!
There are some nice maps online which will help you locate forts.

The Library of Congress also has “Bacon’s military map of the United States shewing forts and fortifications” from 1862.
All in all, I think you will have some fun learning more about the forts that existed near your ancestors’ early settlements, or that they might have lived in as a soldier.
