Columbia subject headings:
Industries--Rocky Mountains Region--History.
Mineral industries--Rocky Mountains Region--History.
Smelting--History.
Harvard subject headings:
Industries--Rocky Mountains Region--History.
Mineral industries--Rocky Mountains Region--History.
Rocky Mountains Region--History.
Smelting--History.
Princeton subject headings:
Mineral industries--Rocky Mountains Region--History.
Rocky Mountains Region--Economic conditions.
Smelting--History.