Airborne electromagnetic (AEM) and magnetic survey data were collected during October 2016 along 1,443 line kilometers in the southwestern San Joaquin Valley near Lost Hills, California. These data were collected in support of groundwater salinity mapping and hydrogeologic framework development as part of the U.S. Geological Survey California Oil, Gas, and Groundwater program and the California State Water Resources Control Board’s Program of Regional Monitoring of Water Quality in Areas of Oil and Gas Production. Minimally processed binary AEM data received from the contractor were imported into the Aarhus Workbench software (v. 5.6.3.0, Aarhus Geosoftware, Aarhus, Denmark) and processed. Filters were applied to inclinometer and spatial positioning data to smooth raw data and remove sensor drop outs. Altimeter data were filtered, smoothed, and manually edited to correct false altitudes associated with trees and other obstacles, resulting in processed altitude representative of the distance between the AEM sensor airframe and bare earth. Ground surface elevations were imported from the 1/3 arc second USGS National Elevation Dataset (U.S. Geological Survey, https://www.usgs.gov/core-science-systems/ngp/3dep/3dep-product-metadata). The elevations were extracted using bilinear interpolation at the intersection of the AEM measurement points and the 1/3 arc second digital elevation model. Raw electromagnetic data were visually examined for couplings and noise associated with infrastructure and considered in the context of the locations of known or suspected infrastructure (power lines, pipe lines, etc...) and magnetic anomalies; impacted data were manually removed. Culled electromagnetic data were averaged using a filter width of 4 seconds applied to high moment and low moment data. Low-signal data were removed from the averaged data through a combination of filters and manual culling. The data provided include fully processed electromagnetic data produced from minimally processed contractor-delivered data, also provided with this data release. The digital data are described in the data dictionary, additional documentation is provided in the metadata.