This data release was prepared as part of an agreement between the California Department of Water Resources (DWR) and the United States Geological Survey (USGS) to support the Sustainable Groundwater Management Act (SGMA). Of the many components of that agreement there is a specific task requiring the Enhancement of Digital Well Completion Reports. Well-completion reports (WCRs) contain information about the wells, such as construction characteristics and lithologic data that is very valuable to SGMA. The data set presented here is a compilation of lithologic information transcribed verbatim from a subset of WCRs contained in the DWR Online System for Well Completion Reports (OSWCR). The format of the lithologic descriptions follows the DWR “free form” entry method which allows for any material description to be entered into the OSWCR without standardization. The lithologic descriptions for all depth intervals recorded (in feet below land surface) by the driller on the WCR are captured verbatim, with no regularization or correction for typographical or spelling errors. Some degree of data processing maybe required by a user of this dataset depending on its intended use. This data release is intended to be updated as new WCRs are transcribed over time. WCR lithologic data featured in version 1.0 focused on WCRs located primarily along the length of the California Aqueduct in the Central Valley of California. WCR lithologic data added in version 2.0 are from select public-supply wells (PSWs). The PSWs included in this update are those which have had their locations refined and construction characteristics captured as part of the USGS Groundwater Ambient Monitoring and Assessment Program-Priority Basin Project (GAMA-PBP) WCR attribution project. Users can find the list of attributed water supply wells compiled by the GAMA-PBP in Borkovich and others, 2023, https://doi.org/10.5066/P93ICKAF. All attributed values should be verified by reviewing the original WCR which can be retrieved from the California Open Data Portal WCR website: https://data.ca.gov/dataset/well-completion-reports California Water Code Section 13752 allows for the release of redacted copies of well completion reports to the public. DWR is the authoritative source of these data. Version 1.0 posted March 28, 2023 Version 2.0 posted June 14, 2024 Changes in version 2.0 1) Lithologic data captured from 4,832 well completion reports have been added to the previously published data set. 2) Additional previously unpublished data for well completion reports included in version 1.0 identified while compiling version 2.0 are also included in this update. 3) Added a new column to the data table that contains the publication date for each entry to help track version history. 4) Updates author information to include users who have contributed to the compilation effort following the publication of version 1.0. 5) Some minor revisions were made to the text of the first process step to improve clarity.