Historical water and gas chemistry data from geothermal areas are important for detecting long-term patterns, informing geothermal energy exploration, development, and use, and for contextualizing more recent data. The U.S. Geological Survey has published water and gas chemistry data from geothermal areas in the western United States, which is primarily available as scanned PDF files. This makes the data difficult to access or include in large-scale data analysis. This data release provides digitized and reformatted data from 20 previously published U.S. Geological Survey Open-File reports and journal articles, representing 1867 water chemistry samples and 313 gas chemistry samples. All data have been standardized to the same units, geographic coordinates, and file format. Description of sample site location was improved. Many reports do not report geographic location coordinates; those that do are frequently inaccurate, as latitude and longitude were interpolated from a map, or in some cases, estimated in the field before the common use of global positioning systems (GPS). Collection dates for individual samples range from 1930 to 2005, although most samples were collected between the years 1970 and 2000. Samples are primarily from California, Oregon, and Washington, although some reports include data from sites in Montana, Idaho, Nevada, Utah, Arizona, and New Mexico. Attributes for both water and gas chemistry are: Sample name, Sample ID, Type, Collection date, Collection time, Reported location, Reported latitude, Reported longitude, Reported Easting, Reported Northing, Location description, Region, State, County, Latitude, Longitude, Location resolution, Location error, Elevation, Source, Author comment, and Digitizer comment. Attributes for water chemistry are: Well depth, Collection depth, Discharge, Temperature, pH (field), pH (lab), pH, Aluminum (Al), Arsenic (As), Boron (B), Barium (Ba), Bromide (Br), Calcium (Ca), Chloride (Cl), Carbonate (CO3), Alkalinity as carbonate (CO3), Cesium (Cs), Copper (Cu), Dissolved Organic Carbon as Carbon (DIC as C), Fluoride (F), Iron (Fe), Hydrogen sulfide (H2S), Bicarbonate (HCO3), Alkalinity as bicarbonate (HCO3), Carbonic acid (H2CO3), Mercury (Hg), Iodide (I), Potassium (K), Lithium (Li), Magnesium (Mg), Manganese (Mn), Molybdenum (Mo), total Nitrogen (N), Sodium (Na), Ammonium (NH4), Nickel (Ni), Nitrate (NO3), total Phosphorus (P), Lead (Pb), Phosphate (PO4), Rubidium (Rb), Silica (SiO2), Sulfate (SO4), Strontium (Sr), Uranium (U), Vanadium (V), Zinc (Zn), Reported cations, Reported anions, Cations, Anions, Reported total dissolved solids, Salinity, Charge balance, Specific conductance, isotopic composition of hydrogen (Delta 2H), isotopic composition of oxygen in water (Delta 18O (H2O)), Oxygen shift, isotopic composition of oxygen in sulfate (Delta 18O (SO4)), isotopic composition of carbon (Delta 13C), isotopic composition of carbon in dissolved inorganic carbon (Delta 13C (DIC)), Tritium (3H), and 14C. Attributes for gas chemistry are: Temperature, Total gas, argon (Ar), oxygen and argon (O2 + Ar), ethane (C2H6), methane (CH4), carbon dioxide (CO2), hydrogen (H2), hydrogen sulfide (H2S), helium (He), nitrogen (N2), ammonia (NH3), oxygen (O2), dissolved argon (Ar dissolved), dissolved methane (CH4 dissolved), dissolved carbon dioxide (CO2 dissolved), dissolved hydrogen (H2 dissolved), dissolved helium (He dissolved), dissolved nitrogen (N2 dissolved), dissolved ammonia (NH3 dissolved), dissolved oxygen (O2 dissolved), isotopic ratio of helium (3He/4He), isotopic ratio of helium corrected for the atmospheric isotopic composition of helium (3He/4He corrected), isotopic composition of nitrogen (Delta 15N), and isotopic composition of carbon in carbon dioxide (Delta 13C (CO2)).