Nitrogen oxides (NO_x = NO + NO₂) play a critical role in regulating tropospheric chemistry, yet NO_x emission estimates are subject to large uncertainties, casting doubt on our ability to accurately model secondary pollutants such as ozone and fine particulate matter (PM_2.5). In previous work, we have established the use of nitrate wet deposition (NWD) fluxes as a reliable proxy for NO_x emissions and trends. Using NWD observations and the chemical transport model GEOS-Chem, we found evidence of NO_x overestimates in emissions inventories over the United States and Europe. Adjusting NO_x emissions based on NWD fluxes over Europe improved model representation of surface ozone, reducing overestimates by 12%. In this work, we aim to expand our established method to new areas, seasons, and pollutants. Specifically, we constrain seasonal NO_x emissions over the Midwestern United States (MWUS) using the National Atmospheric Deposition Program (NADP) NWD fluxes and GEOS-Chem. GEOS-Chem exhibits large biases in ozone and PM_2.5 concentrations on a seasonal basis. Over the MWUS, wintertime PM_2.5 and summertime ozone are overestimated by 35% and 52% on average, respectively. A common thread underlying model biases of both pollutants is uncertainty in NO_x emissions, which are likely overestimated in this region. Our goal is to constrain seasonal NO_x emissions to improve model representation of both ozone and PM_2.5. Our preliminary results suggest that reducing summertime NO_x emissions in the Community Emissions Data System (CEDS) inventory by 60% reduces model overestimates of summertime ozone by 49% across the MWUS. Reducing wintertime NO_x emissions in CEDS by 40% reduces PM_2.5 overestimates by 8%. Future work includes exploring additional constraints on ammonia and sulfur dioxide emissions using ammonium and sulfate deposition to further improve representation of modeled PM_2.5 and its chemical speciation.