The Big Cottonwood area lies in the highest portion of the Wasatch Mountains southeast of Salt Lake City. It contains exposed geologic features developed during two billion years of earth history. Discoveries of small but rich mineral deposits within the area led to a colorful, moderately productive, century-long period of metal mining. While there is no mining activity in the Big Cottonwood mining district today, the area is of considerable interest to students of regional geology and to numerous visitors to the mountain recreational areas. Major thrust faulting is well exposed in outcrops and in mine workings and is of economic importance on a regional scale. The unusual occurrence of the major ore bodies, at the intersections of steep fissure veins with several overthrust planes, similar to that of deposits mined in the adjoining Little Cottonwood (Alta) and American Fork districts to the south, is a classic regional feature. The small deposits in the older Precambrian rocks at the eastern edge of the district present features not seen elsewhere in the state. This report presents new detail on these and other aspects of the geology of the district, and records available geology and history of the many formerly-active underground mines. It presents an update on regional geology. It is written for readers of many interests, not merely for economic geologists. 98 pages + 4 plates