Most studies of the impacts of global warming policy have been performed at the national level. However, national averages obscure the fact that some regions may be affected much more than others. We formulated a regional computable general equilibrium model to analyze the impact of a carbon tax on the Pennsylvania economy. The model incorporates special features relating to labor mobility, trade and energy substitution for this purpose. Our results indicate significant negative overall impacts on the Pennsylvania economy, primarily because it is a major producer and user of fossil fuels, especially coal, and because it is highly industrialized. Sensitivity analyses on key parameters and model assumptions indicate that our results are robust.