Fort Grant Area
Fort Grant is where the "Bloody" 7th Cavalry was stationed. It was built in 1872 and commanded by Lt. Col George Crook. ERB was stationed there from 1896-1897.
The Cave: this is where Captain Carter flees to from the Apaches, and somehow teleports to Mars.
Safford: the town where Captain Carter goes to get supplies.
Apache Camp: where Carter's friend is captured and taken to.
The opening chapter of A Princess of Mars actually takes place in the White Mountains, which are a bit north of Fort Grant. Of course GM's could have the adventure take place from there instead. I found Fort Grant to be a more fascinating location to start a western in since there is a lot of recorded history such as Billy the Kid who killed a man for coughing or spitting on him in Bonita which started off his criminal career.
Cottonwood will be turned into a hive of scum and villainy for the adventure locale.
I'm working out a western character class like a Gunslinger or a Cavalryman or something to go with the adventure, but this tempts me to make a mini western RPG.