Ground-water levels are measured periodically in a network of about 280 observation wells in Wyoming, mostly in areas where ground water is used in large quantities for irrigation or municipal purposes. The program is conducted by the U.S. Geological Survey in cooperation with the Wyoming State Engineer and the city of Cheyenne. This report contains maps showing the locations of selected wells, tables listing well histories and highest and lowest water levels for the period of record, and hydrographs for most of the wells. (USGS)