This report and associated dataset, contains subsurface geologic information collected in the Sacramento-San Joaquin Valley. The primary data includes X, Y, Z locations of stratigraphic horizons and, to a much lesser extent, geologic structures where penetrated by oil and gas wells in the subsurface as recorded in well logs and well records. Selected oil and gas wells are not only examined for depth to stratigraphic horizon data, but also marked if deviated from vertical, or containing specific electronic logs that may be used for geophysical research. The data was compiled from well records made available through the California Department of Conservation, Geologic Energy Management Division (CalGEM) Well Finder web interface. Well Finder provides a map view of wells and fields with links to well records in the CalGEM database. Select records for wells in the study area (principally the well data report, which is a PDF copy of all the forms and associated "paperwork" filed with CalGEM and its predecessor state agencies, and the standard Spontaneous-Potential/Resistivity/Conductivity electric log) were requested, downloaded, and examined. Measurements of depth to geologic features (horizons) such as top or bottom of a geologic unit that are recorded in the well records were compiled into the data set, along with information about the location and identity of the well, and whether the well records available include other types of well log that are commonly of interest to 3D mappers. We also recorded if the well record mentioned that the well is deviated (not entirely vertical), which would affect the true X,Y,Z location of recorded horizons. However, we did not attempt to correct the data to account for the deviation. The values in the data set are those recorded in the well records. We also harvested the same information from the previously published USGS Open-File Report 2011-1262 (Brabb, 2011). Where there are many wells close together, we examined well records until finding a well with a relatively large suite of horizon depths recorded, and then used that well as representative of the many closely spaced wells. The goal was to get a good representation of the regional subsurface, not to record every well. In addition, we did not record all the information available in the well records for those wells in this dataset. The full records are freely available from the data sources. This dataset includes specific information compiled for the purpose described below. The information in this metadata file mainly describes the details of the contents and formats of the digital files.