<>Atmospheric deposition of sulfur and nitrogen compounds (known as acid deposition) has adversely impacted the forest and aquatic ecosystems in North America, Europe, and Asia. In the United States, following the implementation of the Clean Air Act and the subsequent rules, there has been a marked decline in emissions of acidifying compounds (SO₂ and NO_x) resulting in a concomitant decrease in the concentrations of sulfate (SO₄^2–) and nitrate (NO₃⁻) in atmospheric deposition in the eastern United States. Studies indicate that concentrations of SO₄^2– and NO₃⁻ in precipitation at monitoring sites in Northeast were correlated with national emissions of SO₂ and NO_x, respectively. Having historical time series of national emissions, the SO₂ - SO₄^2– and NO_x - NO₃⁻ relationships can be used to hindcast the time series of historical depositions. The accuracy of the hindcasted historical depositions depends on how strongly the current national emissions are related to the current monitored depositions. In this study, we generated an algorithm to develop regression model between national emissions of SO₂ and NO_x and concentrations of SO₄^2– and NO₃⁻ in precipitation at each individual 263 National Atmospheric Deposition Program (NADP) sites throughout the US. We visualized the spatial patterns of correlation coefficients between emissions and deposition concentrations for all NADP sites in the continental US. The time series of reconstructed historical atmospheric deposition can be used as an important input to ecosystem effects models. In the second phase of this study, we evaluated the spatial pattern of dry to wet deposition ratios throughout the US. Currently CASTNET program provides an estimate of atmospheric dry deposition for about 100 sites throughout the US by using modeled dry deposition velocity and the measured air quality concentrations. As the monitoring stations of dry and wet depositions are distributed at different locations, we used an algorithm to calculate dry to wet ratio for the paired stations with the closest distance. We computed dry to wet ratios for all major cations and anions and visualized the spatial patterns of these ratios for the entire US sites.