During water years 2016–2023 (a water year is the period from October 1 to September 30 and is designated by the year in which it ends), the U.S. Geological Survey (USGS), in cooperation with the Illinois Environmental Protection Agency (Illinois EPA), operated continuous monitoring stations on eight of the major rivers in Illinois to better quantify nutrient and sediment loadings from the State of Illinois to the Mississippi River. This data release presents estimates of daily nitrate, phosphorus, and suspended sediment concentrations and uncertainty over that period. The concentration estimates are based on a combination of discrete sampling and surrogate regression (imputation); see Hodson and others (2021) for details on the imputation model. The data release comprises a comma-separated values (csv) file containing daily timeseries of concentration and uncertainty for each monitoring station and a spreadsheet (xlsx) with yearly loads and streamflow for each individual site and total Illinois loads and streamflow. These methods are discussed in the most recent Illinois Nutrient Loss Reduction Strategy Biennial Report pages 25–26 ; see Biennial Report 2021–22 (2023). References Cited: Hodson, T.O., Terrio, P.J., Peake, C.S., and Fazio, D.J., 2021, Continuous monitoring and Bayesian estimation of nutrient and sediment loads from Illinois watersheds, for water years 2016–2020: U.S. Geological Survey Scientific Investigations Report 2021-5092. [Also available at https://doi.org/10.3133/sir20215092]. Illinois Nutrient Loss Reduction Strategy Biennial Report 2021-22. (2023). Illinois Environmental Protection Agency and Illinois Department of Agriculture; Springfield, Illinois. University of Illinois Extension; Urbana-Champaign, Illinois. https://epa.illinois.gov/topics/water-quality/watershed-management/excess-nutrients/nutrient-loss-reduction-strategy.html.