This data release is a geochemical data set from the reanalysis of 23 rock and 85 sediment samples collected between 1966 and 1970 by the U.S. Geological Survey (USGS) for a series of studies investigating the mineral resources of the Idaho Primitive Area (Cater et al., 1973). The samples are from the upper Middle Fork Salmon River and the South Fork Salmon River, including the tributaries of East Fork of the South Fork and Porphyry Creek. The overall objective of this study is to characterize the regional impact of legacy mining for the Frank Church - River of No Return Wilderness Area. In 1980 the U. S. Congress passed the Central Idaho Wilderness Act which combined the Idaho Primitive Area, the Salmon Rivers Breaks Primitive Area, and other wilderness into the River of No Return Wilderness Area. Frank Church was added to the name in 1984 changing it to the Frank Church - River of No Return Wilderness with the signing of legislation in 1984 (USDA Forest Service, 2001). Stream sediment and rock samples collected for the USGS Idaho Primitive Area mineral resource assessment is summarized in Granitto and Lund (2020). The samples collected in 1966-1970 were analyzed using semiquantitative spectrographic methods for major and trace elements. Some samples were analyzed by wet chemical methods for cobalt while arsenic, copper, and heavy metals were analyzed for all sediments and some mineralized rocks. These methods did not produce data for the total element concentration of the sample. Samples containing large amounts of rare-earth elements were analyzed by quantitative emission spectrography. Samples were analyzed in several U.S. Geological Survey laboratories over a 4-year period using different analytical techniques. These techniques were modified and refined during this period (Cater et al., 1973). Consequently, not all the reported results summarized are directly comparable. A subset of the archived materials was reanalyzed using current standard methods for consistency allowing comparability for all elements. Analytical techniques used for the reanalyzed samples reported here include a 60-element analysis following a sodium peroxide fusion by either inductively coupled plasma-optical emission spectrometry (ICP-OES) or inductively coupled plasma-mass spectrometry (ICP-MS). Arsenic was also determined using hydride generation atomic absorption spectrometry (HGAAS) following a sodium peroxide fusion since the arsenic detection limit is 10 times lower for this technique. Thus, these new data for archived sediment and rocks from the Middle Fork and South Fork of the Salmon River are internally consistent and directly comparable. References cited above: Cater, F.W., Pickney, D.M, Hamilton, W.B, Parker, R.L., Weldin, R.D., Close, T.J., and Zilka, N.T., 1973, Mineral Resources of the Idaho Primitive Area and Vicinity, Idaho: Geological Survey Bulletin 1304, p. 445. USDA Forest Service, 2001, A User's Guide Frank Church - River of No Return Wilderness, Frank Church River of No Return Wilderness, Salmon, Idaho, p. 39. Granitto, M., and Lund, K., 2020, Geochemical Data Release for Idaho Primitive Area, including the contiguous Clear Creek-Upper Big Deer Creek Area, the Salmon River Breaks Primitive Area, the Sawtooth Primitive Area, and adjacent areas, central Idaho: U.S. Geological Survey data release, https://doi.org/10.5066/P9BT11RJ.