This digital dataset is comprised of two separate data files that contain total dissolved solids, well construction, and well identifying information for 1,131 petroleum wells used to map salinity in and around 31 southern and central California oil fields. Salinity mapping was done for 27 fields located in the southern San Joaquin Valley of Kern County (North Belridge, South Belridge, Canfield Ranch, North Coles Levee, South Coles Levee, Cymric, Edison, Elk Hills, Fruitvale, Greeley, Jasmin, Kern Bluff, Kern Front, Kern River, Lost Hills, Mount Poso, Mountain View, Poso Creek, Rio Bravo, Rosedale, Rosedale Ranch, Round Mountain, San Emidio Nose, Tejon, Ten Section, Wheeler Ridge, and Yowlumne), 3 fields in the Los Angeles (LA) Basin of Los Angeles County (Montebello, Santa Fe Springs, and Wilmington), and 1 field in the central coast area of Santa Barbara and San Luis Obispo Counties (Santa Maria Valley). Only petroleum wells that were located within the administrative boundaries of these 31 fields were used for salinity mapping. The dataset includes total dissolved solids (TDS) analyses from 1930 to 2015. TDS data for each well varies from a single analysis to multiple analyses for different sample dates and (or) collected from different depths within the same well. For wells having multiple analyses TDS represents the median value. There are 159 wells in the dataset each having 2-4 TDS analyses, including 15 wells having TDS values from different depths. This dataset also includes ancillary data in the form of top perforation depth, land-surface elevation at the well head, and well location and identifier information. For petroleum wells missing top perforation depth (3 percent), the median top perforation depth for all wells within the field having top of perforation depth is provided as an approximation for the purpose of vertical plotting. Summary data about each well used for salinity mapping is contained in the file called Petroleum_Wells_Summary_Data. Detailed information about all individual TDS values including those used for determining median TDS values, are contained in the file called Petroleum_Wells_All_Data.