This data release contains tabular digital data describing calculated hourly back trajectory position coordinates for air masses contributing to five selected precipitation-mercury deposition episodes at National Atmospheric Deposition Program monitoring site IN21 (National Atmospheric Deposition Program, 2017) in southeastern Indiana during 2009‒2015. The air pollution transport and dispersion modeling system HYSPLIT (Stein et. al, 2015) was used to calculate the back trajectory position coordinates during 48 hours preceding the start of each episode. The 40-km gridded input data to HYSPLIT were from National Oceanic and Atmospheric Administration (2017). Continuous, digital precipitation depth data were recorded at the IN21 monitoring site. Each episode was defined as containing hourly precipitation depth totals > 2.54 mm (0.10 inch) and a precipitation-mercury deposition amount between 1,640 and 2,158 nanograms per square meter per week. Back trajectories were plotted from starting heights of 100 m, 300 m, and 500 m above ground level. These trajectories were not constrained and the actual height of the air mass as it traveled could vary from ground level to the boundary layer at 1,000 m to 2,000 m. References cited: National Atmospheric Deposition Program, 2017. Mercury Deposition Network. Accessed 2017 at http://nadp.sws.uiuc.edu/mdn/ National Oceanic and Atmospheric Administration, 2017. Eta Data Assimilation System (EDAS40) Archive Information. Accessed 2017 at https://www.ready.noaa.gov/edas40.php and ftp://arlftp.arlhq.noaa.gov/pub/archives/edas40/ Stein, A.F., Draxler, R.R, Rolph, G.D., Stunder, B.J.B., Cohen, M.D., and Ngan, F., 2015. NOAA's HYSPLIT atmospheric transport and dispersion modeling system, Bull. Amer. Meteor. Soc. 96, 2059-2077. http://dx.doi.org/10.1175/BAMS-D-14-00110.1