Fred Diamond has a simple set of free wargames rules for playing the Indian Wars in the America of the late 19th century.
wild west
Plains Indian Horse Symbols
I’m currently painting some of Wargames Foundry’s Plains Indians for a 7th Cavalry game. I found this site, with descriptions of symbols that the Native American warriors painted on their horses.
Simple Solo Wargames Rules For The Wild West
Mark Ainsworth offers a set of simple solo wargames rules for games of the 7th Cavalry against Plains Indians.
Tombstone RPG
Tombstone is a free RPG set in the wild west. It’s designed to be rules-light, and has quick play character creation to get you started.
Black Hat, White Hat
Black Hat, White Hat is a set of free wargames rules for Wild West skirmishes.