The U.S. Geological Survey National Water Information System (NWIS) data archive contains publicly available water-quality data for approximately 20,000 groundwater wells and springs in California. This data release publishes site type information and a generalized use classification for the sites. The generalized use category is derived from, but is not equivalent to, the use of site and use of water fields from the NWIS data archive. The use of site and use of water fields in the NWIS data archive are not publicly available. The 20,000 groundwater wells and springs were categorized as into seven generalized use categories: 1) domestic, 2) irrigation, 3) production, 4) water supply, other, 5) observation, 6) other, and 7) unknown. A similar classification system was used by Stork and Fram (2021) to categorize sites sampled by the USGS for the California State Water Resources Control Boards' (SWRCB) Groundwater Ambient Monitoring and Assessment Program Priority Basin Project (GAMA-PBP). The classification presented here only uses information from the use of site and use of water fields in the NWIS data archive; the classification presented by Stork and Fram (2021) considered additional information collected by the GAMA-PBP about the sites. USGS NWIS 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 groundwater sites in NWIS, except those sampled by the GAMA-PBP, as "water supply, other", which resulted in erroneous characterization of approximately 98 percent of the sites. The generalized use 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.