This data release provides preliminary estimates of annual agricultural use of pesticide compounds in counties of the conterminous United States, for the year 2018, compiled by means of methods described in Thelin and Stone (2013) and Baker and Stone (2015). For all States except California, U.S. Department of Agriculture county-level data for harvested-crop acreage were used in conjunction with proprietary Crop Reporting District-level pesticide-use data to estimate county-level pesticide use. Where Crop Reporting District data were not available or were incomplete, estimated pesticide-use values were calculated with two different methods, resulting in a low and a high estimate based on different assumptions about missing survey data (Thelin and Stone, 2013). Pesticide-use data for California were obtained from the California Department of Pesticide Regulation Pesticide Use Reporting (DPR–PUR) database (California Department of Pesticide Regulation, 2020). The California county data were appended after the estimation process was completed for the rest of the Nation. Preliminary estimates in this dataset may be revised upon availability of updated crop acreages in the 2022 Agricultural Census, expected to be published by the U.S. Department of Agriculture in 2024. Estimates of annual agricultural pesticide use are provided as downloadable, tab-delimited files, organized by compound, year, state Federal Information Processing Standard (FIPS) code, county FIPS code, and amount in kilograms. Tables of annual agricultural pesticide-use estimates beginning in 1992 are available for download on the Pesticide National Synthesis Project webpage: https://doi.org/doi:10.5066/F7NP22KM. References cited: Baker, N.T., and Stone, W.W., 2015, Estimated annual agricultural pesticide use for counties of the conterminous United States, 2008–12: U.S. Geological Survey Data Series 907, 9 p., accessed July 12, 2015, at https://doi.org/10.3133/ds907. California Department of Pesticide Regulation, 2020, Pesticide use reporting (PUR): California Department of Pesticide Regulation Pesticide Use Reporting (PUR), Pesticide Use Report Data (PUR archives pur2018.zip), accessed December 29, 2020, at http://www.cdpr.ca.gov/docs/pur/purmain.htm. Thelin, G.P., and Stone, W.W., 2013, Estimation of annual agricultural pesticide use for counties of the conterminous United States, 1992–2009: U.S. Geological Survey Scientific Investigations Report 2013–5009, 54 p., accessed July 12, 2015, at http://pubs.usgs.gov/sir/2013/5009/.