Few regions have had as long, interesting, and complicated a history of exploration for mineral resources, particularly petroleum, as the Arctic Slope of Alaska. In 1923 President Harding, anticipating a need for oil for the U.S. Navy, set aside the western half of the Arctic Slope as Naval petroleum Reserve No. 4 (NPR-4), more recently redesignated as the National Petroleum Reserve in Alaska (NPRA). Exploration by both the federal government and industry continued, culminating in 1968 in the discovery of North America's largest oil field at Prudhoe Bay. The Naval Petroleum Reserves Production Act of 1976 transferred the responsibility for the newly redesignated NPRA to the Department of the Interior (DOI), directed the continuation of the exploration programs, and mandated a series of studies on all the resources and future management of the Reserve. Geophysical surveys were completed for the entire Reserve, more than 22,500 line kilometers (14,000 miles). Test wells were drilled systematically in all areas of the Reserve on the basis of prospective geologic models or plays. Additional gas deposits were discovered in the Barrow area, and oil shows appeared in many of the tests. However, no major petroleum deposits were discovered. All of the geological and geophysical information that was collected during the exploration program supervised by the USGS from 1976 to 1982 was released to the public as it was accumulated and organized. The publication of the present volume summarizes much of this information and documents several ongoing USGS research projects that were begun during the exploration program or that have special significance to the geology of the NPRA. Thirty-nine chapters have been indexed separately.