This data release provides a digital inventory of the Robert S. Thompson packrat midden collection consisting of 1,740 midden samples and subsamples primarily collected in the Great Basin region of Nevada, as well as in Arizona, California, Colorado, Oklahoma, Utah, and Washington, USA, by Robert S. Thompson (USGS scientist emeritus) and others between 1977 and 2006. Middens are waste piles composed of the urine and feces of packrats (Neotoma spp.) also containing plant materials, bones, and insects. Radiocarbon dating of middens indicates they can be preserved for as long as 50,000 years, and their fossil plant assemblages document changes in plant community composition through time, providing important records of paleoenvironmental change in western North America during the late Pleistocene and Holocene. Middens are valuable non-renewable paleoecologic resources, and once collected, middens and their contents cannot be reproduced. Since middens are one-of-a-kind, limited resources, it is critical to preserve specimens for future research. Upgrades to midden storage materials for long-term sample preservation, improved organization, and a digital sample inventory of the R.S. Thompson collection now provide opportunities for further study of plant fossil materials and paleoenvironmental change, as well as opportunities for novel midden-based research in fields such as evolutionary biology, genetics, biochemistry, and ecology. Middens also provide ideal materials for the application of new and advanced techniques in microscopy, age dating, and DNA analysis. Digital inventory data tables include, midden sample site location data, and descriptions of sample materials (unwashed, washed, or sorted) and midden contents (e.g., wood, seeds, or conifer needles). New specimen labels use unique collection IDs to identify samples/subsamples, which also correspond to midden samples documented in the USGS North American Packrat Midden Database, version 5.0 (Strickland and others, 2022, 2024) where additional data (plant macrofossil taxon lists and radiocarbon ages) can be accessed for some samples in the collection. The R.S. Thompson midden collection inventory is available as tabular (.xlsx) and comma-separated value (.csv) files.