Monitoring the chloride (Cl) flux in the major rivers draining Yellowstone National Park (YNP) provides a holistic view of the thermal output from the underlying magma reservoir, and abrupt fluctuations in the Cl flux may signify changes in hydrothermal activity. The U.S. Geological Survey (USGS) and the National Park Service (NPS) have collaborated on Cl flux monitoring of the major rivers since the 1970s. In the past, researchers collected water samples from the major rivers in YNP, but funding restrictions, winter conditions, and the great distances between sites limited the number of samples collected annually. Beginning in 2010, specific conductance, which is relatively easy to measure and can be automated, has been used as a proxy for Cl. The use of specific conductance probes at the various monitoring sites enables a more consistent estimation of Cl flux. Consistent monitoring is useful to identify changes in river chemistry due to geyser eruptions, rain events, or changes in thermal inputs caused by earthquakes or other natural events. The use of specific conductance as a proxy for Cl requires quantification of the relationship between specific conductance, Cl, and other geothermal solutes and the relationship needs to be periodically verified. This data release contains specific conductance measurements (every 15 minutes) and water chemistry data from monitoring sites along the Madison River, Firehole River, Gibbon River, Snake River, Gardner River, Fall River, Yellowstone River, and Tantalus Creek. For several sites, there are periods of time when specific conductance is not reported because the data was likely unreliable due to failure or fouling of the specific conductance probe. There are also specific conductance and discharge data available from the USGS National Water Information System (USGS NWIS, https://waterdata.usgs.gov/nwis/rt). The following list details the sites included in this data release and the National Water Information System site identification numbers. Yellowstone River near Corwin Springs, 06191500; Gardner River near Mammoth, 06191000; Firehole River near West Yellowstone, 06036905; Firehole River at Old Faithful, 06036805; Fall River near Squirrel, Idaho, 13046995; Gibbon River at Madison Junction, 06037100; Madison River near West Yellowstone, 06040000; Snake River near Flagg Ranch WY, 13010065; and Tantalus Creek at Norris Junction, 06036940. First posted - January 28, 2019 (available from author) Revised - May 6, 2020 (version 2.0) NOTE: While previous versions are available from the author, all the records in previous versions can be found in version 2.0.