Seven Mile Number 1 Reservoir is a reservoir located in Niobrara County, Wyoming. It appears on the Threemile Butte USGS 7.5-minute topographic quadrangle. The elevation at this location is approximately 3,826.06 feet (1,166.18 m) above sea level. The nearest populated place is Morrisey, approximately 7.4 miles to the NNE.