From introduction: This report contains information concerning the geology of Big Horn County and the Crow Indian Reservation and their resources in ground water, coal, oil, and gas. These facts were collected in the course of studies for about a dozen field projects, which ranged in character from reconnaissance studies of large areas to very detailed mapping of certain tracts to show the occurrence of oil and gas. Consequently, the information at hand, either as to the geology or the resources, is not equally complete and definite for all parts.