1. Geologic map of the Scenic area, Pennington, Shannon, and Custer counties, South Dakota Yale Public content 1971. 2012-11-07T20:57:13Z. 2012-11-07T20:57:13Z. King, Robert Ugstad, 1912-. U.S. Geological Survey. English. Public. South Dakota, Pennington County, Shannon County, and Custer County.