Cover cropping is one of the most promising conservation practices to mitigate climate change and improve soil health. However, the overall adoption rate of cover crops remains low across the Midwestern U.S., partially due to their high cost of adoption and insufficient financial incentives from the government and private programs. While cover crops are frequently observed to improve soil health, the climate, soil, and management interactions have limited our ability to quantify these benefits at the regional-scale as cover crop adoption rate increases. Accurate quantification of soil carbon benefits and nitrate leaching reduction at the regional scale has been particularly challenging. Therefore, we used a process-based ecosys model to assess the benefits of cover crops on soil organic carbon accumulation, nitrogen leaching reduction and on potential corn and soybean yield. We first calibrated the model with cover crop biomass, cash crop yield, soil carbon concentration, and nitrogen leaching through paired field observations (i..e, with and without cover crop). We then validated ecosys with distributed field-measured cover crop biomass data at the regional scale. After rigorous calibration and validation, we applied the ecosys model to simulate cover crop impacts at the regional scale for the U.S. Corn Belt. Specifically, we compared several cover crop scenarios for each field with different cover crop types (i.e., legume and non-legume cover crops) and termination times (i.e., 1, 7, 14, 28 d before cash crop planting). Through the analysis, we quantified SOC benefits and nitrogen leaching reduction benefits from cover crops with different cover crop adoption rates (i.e., 10%, 30%, 50%, 70%). To reveal the impacts of different factors on cover crop growth and cover crop benefits, we assessed driving factors including initial soil conditions (i.e., clay content, SOC stock), climate conditions (i.e., temperature and precipitation) and cover crop management practices (i.e., cover crop species, cover crop growth window and fertilizer rates) through regional pattern analysis. Overall, the study revealed that cover crops hold great potential for climate change mitigation and improved soil health in the U.S. Corn Belt, and there is large potential to expand cover crop adoption rates.