Well and chemical groundwater data contained in two tables were collected during a 3-yr study started in 1964 to determine the geology and water resources of Campbell County, South Dakota. Physical, hydrologic, and geologic data for 631 wells and test holes have been entered into computer storage in the Groundwater Site Inventory File of the U.S. Geological Survey 's National Water Data Storage and Retrieval System (WATSTORE). The well table in the report is a computer printout from WATSTORE. Water quality data from 257 chemical analyses have been stored in the Water Quality File of WATSTORE and is computer printed in the chemical table by aquifer. (USGS)