This U.S. Geological Survey (USGS) Data Release provides data from samples and measurements completed at the National Crude Oil Spill Fate and Natural Attenuation Research Site near Bemidji, Minnesota (Site) since 1983. This is version 3.0 of this data release, and it now contains 11 data sets. The content of these data sets include inorganic and organic chemistry data from water, oil, and sediment samples, hydraulic conductivity data from well slug tests, sediment grain-size distribution data from core samples, and water- and oil-level data. Most of these data sets have been described in previously published peer-reviewed reports. This data release provides data sets that were not included with the original publications in a tabular, database-ready format. Each result value in the data sets is coded to describe the kind of sample collected, the material that was analyzed, the method of analysis, and the publication where the value was originally published. Some sample codes are taken from the U.S. Geological Survey's National Water Information System (NWIS, https://waterdata.usgs.gov/nwis) and the remaining codes were developed specifically for Site data. Data dictionaries containing code definitions are available at a companion data release titled "Sampling site information, well construction details, and data dictionaries for data sets associated with the National Crude Oil Spill Fate and Natural Attenuation Site near Bemidji, Minnesota", available at https://doi.org/10.5066/F7736PDR. The National Crude Oil Spill Fate and Natural Attenuation Research Site is located where a high-pressure pipeline carrying crude oil burst in 1979 and spilled approximately 1.7 million liters (10,700 barrels) of crude oil into glacial outwash deposits. Since 1983, scientists with the U.S. Geological Survey, in collaboration with scientists from academic institutions, industry, and the regulatory community have conducted extensive investigations of multiphase flow and transport, volatilization, dissolution, geochemical interactions, microbial populations, and biodegradation with the goal of providing an improved understanding of the natural processes limiting the extent of hydrocarbon contamination. Long-term field studies at Bemidji have illustrated that the fate of hydrocarbons evolves with time, and a snap-shot study of a hydrocarbon plume may not provide information that is of relevance to the long-term behavior of the plume during natural attenuation. The research at the site has been supported primarily by the U.S. Geological Survey's Toxic Substances Hydrology Program.