This paper reports the results of policy simulations of environmental and human health externalities arising from the production of electricity. The primary purpose of this paper is to illustrate the Maryland Externalities Screening and Valuation Model, developed for the State of Maryland's Department of Natural Resources. A secondary purpose is to estimate likely Maryland benefits from Title IV emissions reductions at electric power generation facilities. Sources and scope of benefits, and the potential of policy to achieve specific environmental and human health goals, are suggested by the results. We find that expected health benefits from reductions in power plant emissions dominate the estimated benefits of improved recreational visibility and residential visibility. The latter are the only environmental benefits the model is currently equipped to estimate, because of gaps in the science-to-economics literature. The model fully accounts for all significant environmental pathways, so future parameter estimates can be inserted as they are developed. We estimate that in 2010 Maryland health benefits will be about $0.7 billion, while recreational visibility benefits (in Shenandoah National Park) will be approximately $21 million (to residents of Virginia and Maryland), and residential visibility benefits, for inhabitants of a city of the size of Washington, DC and similarly affected by reduced urban visibility, will be about $1.2 million. This integrated-assessment model is designed to estimate and report also the tremendous uncertainties in measuring and valuing these effects.