This dataset presents the total estimated monthly public-supply water withdrawal by 12-digit hydrologic unit code (HUC12) in the conterminous United States for 2015. Public-supply water use was estimated by spatially and temporally downscaling available data from each state. The total represents combined groundwater and surface water withdrawals for 83,178 watersheds. Public supply refers to water withdrawn by public and private water suppliers that provide water for cities, towns, rural water districts, mobile-home parks, Native American Indian reservations, and military bases. Public-supply facilities are classified under the Standard Industrial Classification (SIC) 4941 and provide water to at least 25 people or have a minimum of 15 connections. Water withdrawals are used mostly for domestic purposes, but also serve other customers such as commercial and industrial establishments. These monthly estimates by HUC12 support USGS National Integrated Water Availability Assessments Water Use Maps.