The U.S. Geological Survey collected water-quality samples from 3,199 sites between May 2004 and April 2022 for the California Groundwater Ambient Monitoring and Assessment Program Priority Basin Project (GAMA-PBP). The GAMA-PBP is a cooperative project with the California State Water Resources Control Board (SWRCB). The primary objectives of the GAMA-PBP are: (1) to assess the quality of groundwater resources used for public and domestic drinking water supplies, (2) to develop understanding of the natural and anthropogenic processes controlling groundwater quality and changes in groundwater quality, and (3) to improve the availability and usefulness of groundwater quality information to public. This data release publishes site type information and a generalized use category for the sites. The dataset comprises 3,053 wells, 81 springs, and 65 other types of sites. The generalized use category is partially derived from, but is not equivalent to, the use of site and use of water fields from the USGS National Water Information System (NWIS) data archive. Of the 2,903 wells and springs from which water is withdrawn for use, 1,651 are classified as production (includes sites used for public, commercial, industrial, institutional, and desalination water supplies), 973 as domestic, 264 as irrigation, and 15 as other water supply uses. Of the remaining sites, 225 are classified as observation wells, 6 are wells and springs from which water is withdrawn and not used, 63 are distribution system taps, and 2 are other types of sites. GAMA-PBP data are also served to the public through the SWRCB's GAMA Groundwater Information System (GAMAGIS), along with data from other federal, state, and local agency sources, and the generalized use categories in this data release are compatible with the use categories in SWRCB GAMAGIS. Prior to publication of this data release, SWRCB GAMAGIS classified all GAMA-PBP sites as "municipal", which resulted in erroneous characterization of approximately half of the sites. The generalized classification provided in this data release greatly improves the accuracy of site characterization, while still complying with Federal policies concerning release of location information for some types of sites. Version 1.0 posted September 29, 2021 Version 2.0 posted August 31, 2022 Changes in Version 2.0 1) A total of 143 sites were added to the data release. Seventy-one (71) sites were sampled for the first time by the GAMA-PBP between July 2021 and April 2022 after publication of Version 1.0 of this data release. Seventy-two (72) sites were sampled prior to publication of Version 1.0, but were inadvertently omitted. 2) A new Site_Type, DISTRIBUTION SYSTEM, was added, and a process step was added to describe how and why it is used. Of the 72 sites omitted from Version 1.0, 63 were distribution system sites sampled in 2012-2013. 3) The GAMAIDs for two sites were corrected. Site 342959117133002 is S8-MOBSU-U09 (given as S8-MOBSU-U10 in Version 1.0), and Site 342959117133003 is S8-MOBSU-U10 (given as S8-MOBSU-U09 in Version 1.0) 4) A second GAMAID was added to seven WELL sites that were also sampled as DISTRIBUTION SYSTEM sites under a different GAMAID but the same USGS Site_Number (363700121500001, 365425121452201, 354000120410001, 354501120413301,354911120452701, 360600121000001, 361631121112001) 5) The USE_CATEGORY for 8 sites was changed for consistency with how use of those sites is described elsewhere. Three natural springs and one unused well were changed from the category OTHER to the category OBSERVATION (413600122240001, 383548122360601, 382925122294901, 373738119045501). Four wells were changed from category WATER SUPPLY, OTHER (364800118110001, 382307122311301) or category OBSERVATION (382702122423701, 365000120450001) to category PRODUCTION to reflect that the sites are standby or not currently in use but when the water is used, the use is in the PRODUCTION category. 6) References were added to the process steps to provide the users with links for accessing the water-quality and other data associated with the sites listed in this data release. 7) The counts of site types in the text of the Abstract and Purpose were updated. Version 1.0 can be obtained by request from M.S. Fram (mfram@usgs.gov)