This dataset contains geochemical and other information for 40 historical samples of produced water from the North Coles Levee Oil Field. Three of these samples are from commingled tanks containing produced water from multiple wells as noted in the “Remarks” column. Water that is produced as a byproduct of oil production is called produced water. The numerical water chemistry data were compiled by the U.S. Geological Survey (USGS) from scanned laboratory analysis reports available from the California Geologic Energy Management Division (CalGEM). Sample site characteristics, such as well construction details, were attributed using a combination of information provided with the scanned laboratory analysis reports and well history files from CalGEM Well Finder. The data were transferred manually into a numerical dataset and organized by specific produced water chemical characteristics. Each sample is identified by its API (American Petroleum Institute) number, latitude and longitude, well name, formation name, perforation interval, and date tested. The geochemical analyses include major ions, some minor ions, total dissolved solids (TDS), pH, specific gravity, resistivity, electrical conductivity, and charge balance. The collection and analysis methods and circumstances under which the historical samples were collected cannot be fully known. The intent is to use these historical data in grouped analysis including many sample results, rather than detailed interpretation of each individual sample. Caution should be used in basing interpretations of the data on single sample results.