When handed a rifle, Ben Novack says it's a little bigger than the one he used in Czechoslovakia. Czechoslovakia was not a country until 1918; this movie never states the exact year it takes place but it's clearly in the 1800s.
The scene in the mining office has a map of the United States in the background. The map has modern state borders. At the time when the movie takes place most of the west had large territories.