Columbia subject headings:
Gold mines and mining--United States.
Mines and mineral resources--United States.
Silver mines and mining--United States.
Harvard subject headings:
Gold mines and mining--United States
Gold mines and mining--West (U.S.)
Mines and mineral resources--United States
Mines and mineral resources--West (U.S.)
Silver mines and mining--United States.
Silver mines and mining--West (U.S.)
Princeton subject headings:
Gold mines and mining--United States.
Mines and mineral resources--United States.
Silver mines and mining--United States.