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.
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.