Technical Abstract: A change in cropping and feeding practices can affect the performance, economics and environmental impacts of a dairy farm. A whole farm assessment of all major effects can only be done through process level simulation of the production system. The Integrated Farm System Model provides a research and educational tool for this type of evaluation. A farm production system can be simulated through many years of weather to quantify the performance, economics and environmental effects under the assumed management. Then various changes in cropping and feeding practices can be simulated to determine their effects. Performance measures include crop yield and nutritive value, animal intake and production, machinery use and timeliness of operations, and the use of resources such as fertilizer, fuel, and labor. Production costs, income and net return are then calculated from the simulated performance. Predicted environmental impacts include emissions of ammonia, hydrogen sulfide and greenhouse gases, edge of farm losses of sediment and phosphorus, and leaching of nitrogen and phosphorus to groundwater. From the predicted performance and losses, carbon, energy, water and reactive nitrogen footprints are determined for each production practice. A life cycle assessment is used to determine these footprints, which includes both direct farm sources as well as those occurring in the production of resources used on the farm. This Windows-based software tool is available for research and educational use at https://www.ars.usda.gov/Main/docs.htm?docid=8519. Information obtained through the simulation of various management practices will lead to the selection of more sustainable production systems for dairy production in the Northeast in response to changing climate and economic conditions.