There is need for a reliable and authoritative index measuring the production of minerals in the United States in terms of physical quantity from the time when each of the mineral industries became an important factor in the national economy to the present. It is our hope that the annual index of mineral production for the period 1880 to 1948, together with the indexes for important mineral groups, as described here, will fill this need.1Sixty-three annual physical volume series on mineral production have been selected for inclusion in the index.