Nitrogen deposition has become a major concern for protected ecosystems in the Western US. A “critical load” value for an individual pollutant is defined as the amount of that pollutant an ecosystem can absorb before detrimental changes occur to that ecosystem. Researchers have found that many areas in the Western US have surpassed their critical load for nitrogen deposition. Here we utilize the Comprehensive Air quality Model with Extensions (CAMx) with 2008 meteorology and emissions to simulate the nitrogen deposition in the Western US. These model inputs were generated as part of the WESTJUMP modeling study which included a detailed assessment of oil and gas emissions. We compare modeled nitrogen deposition to critical load values for sensitive lichen species, finding that 73% of class 1&2 areas in the Western US have modeled annual nitrogen deposition totals above these conservative critical load values.  Oil and gas production in the Western US has increased considerably in the past 5 to 10 years, often in remote areas near class 1&2 sensitive ecosystems. We also quantify the modeled contribution of emissions associated with oil and gas production to nitrogen deposition by comparing a 2008 modeling run without oil and gas emissions to the 2008 basecase modeling run with full emissions. We report the contributions of oil and gas to nitrogen deposition in all class 1&2 areas in the Western US in the context of their critical load values.