Information is presented in this report on the production, value, and further development potentials of mineral resources in the Belle Fourche River and Moreau River basins in northeastern Wyoming and northwestern South Dakota. Metals, nonmetals, and mineral fuels other than lignite are found in the Belle Fourchebasin; lignite, sand, and gravel occur in the Moreau basin. Minerals currently produced in the basins include oil and gas, coal, gold, silver, bentonite, clay, lignite, limestone, uranium-vanadium, gypaum, scoria, sand, and gravel. Cumulative output value of the major products-- gold and silver, oil and gas, bentonite, and coal-- now exceeds $1.3 billion.