This 3-sheet map report describes the hydrologic conditions in northwestern Wyoming. The increasing number of tourists and residents and the shifting of overnight accommodations for tourists from Yellowstone and Grand Teton National Parks to nearby areas may result in the need for development of additional water supplies in northwestern Wyoming. Hydrologic data have been collected from wells, springs, streams, and lakes in northwestern Wyoming and are given in maps, tables, and graphs. Using streamflow and water-table data, the transmissivity of a segment of an aquifer in alluvium and glacial outwash in Jackson Hole was estimated to be 30,000 feet squared per day (2,800 meters squared per day). Water in the study area is used for irrigation and for public, domestic, and commercial supplies. (Woodard-USGS)