Recently visited Columbia State Park here in California and talked with one of the rangers a bit and it seems that a lot of the members of the cast of Paint Your Wagon hung out in the town. And it certainly has (had?) the right ingredients to be the inspiration for No Name City. While Mrs. Rumson is certainly the best visual in the film, I'd go with the town information signs as second: "Population: Drunk"
Now that I think of it, the French tarts weren't bad scenery either.
So, I'm up to three films as my primary inspiration for the wild west: Paint Your Wagon, Hallelujah Trail, and Chisum. Do have a few other old west films in the collection - five or six dozen maybe.