The U.S. Geological Survey collected groundwater samples from 38 wells used for domestic and small system drinking water supply in the Coachella Valley of California in 2020. The wells were sampled for the Coachella Valley Basin (CODA) Domestic Aquifer Study Unit of the California State Water Resources Control Board Groundwater Ambient Monitoring and Assessment (GAMA) Program Priority Basin Project’s assessment of the quality of groundwater resources used for domestic and small system drinking water supplies. Coachella Valley is located in the Desert hydrogeologic province (Johnson and Belitz, 2003) and is structurally divided into four subbasins by the San Andreas fault: the Indio subbasin, the Mission Creek subbasin, the Desert Hot Springs subbasin, and the San Gorgonio Pass subbasin (California Department of Water Resources, 2016). These basins have CA basin designations 7-21.01, 7-21.02, 7-21.03, and 7-21.04 respectively. The study area was divided into 30 equal-area grid cells with at least one well sampled in 26 of the 30 cells. This dataset identifies the well locations, study unit boundary, and grid cells for the Coachella Valley Domestic-Supply Aquifer study unit. Note: The only difference between the original version of this data release and this version is that this data release includes results for tritium. Tritium results were not included in the original version because they were not available at the time of publication.