The Groundwater Usage for Public Supply dataset contains attributes pertaining to groundwater use in the glaciated conterminous United States summarized by county. The attributes were computed from total groundwater usage by county compiled by Maupin and others (2010), and from inventories of water-use records for 71,267 public water-supply systems by Buchwald and others (in press). Source aquifers (Quaternary sediments or bedrock) were assigned for the public water-supply systems based on reported data (e.g., well construction records, aquifer delineation maps), or based on well depth and the Quaternary sediment thickness. Water usage rates are reported on an average annual, areal basis in units of millimeters per year, to facilitate comparison with estimated recharge rates from Westenbroek and others (in press).