This dataset contains estimates of water withdrawals from 66 principal aquifers and "other" non-principal aquifers during 2015 for various categories of use in each county or county equivalent in the United States, Puerto Rico, and the U.S. Virgin Islands. The U.S. Geological Survey's (USGS) National Water Use Science Project is responsible for compiling and disseminating the Nation's water-use data. Withdrawal estimates are summarized in USGS Circular 1464, "Estimated Groundwater Withdrawals from Principal Aquifers in the United States, 2015" (Lovelace and others, 2020). This dataset contains the estimated groundwater withdrawals from principal aquifers by county and county equivalent that are summarized by lithologic group, principal aquifer, and state in Lovelace and others (2020). This dataset contains data for public supply, domestic, irrigation, thermoelectric power, industrial, mining, livestock, and aquaculture water-use categories. These data are a further refinement of groundwater withdrawals presented in USGS Circular 1441, "Estimated Use of Water in the United States in 2015" (Dieter and others, 2018). Lovelace, J.K., Nielsen, M.G., Read, A.L., and Murphy, C.J., 2020, Estimated withdrawals from principal aquifers in the United States--County-level data for 2015: U.S. Geological Survey data release, https://doi.org/10.5066/ P9Q3FKGT. Dieter, C.A., Maupin, M.A., Caldwell, R.R., Harris, M.A., Ivahnenko, T.I., Lovelace, J.K., Barber, N.L., and Linsey, K.S., 2018, Estimated use of water in the United States in 2015: U.S. Geological Survey Circular 1441, 65 p., https://doi.org/10.3133/cir1441.