This paper examines the extent of variation in regulatory stringency below the state level, using establishment-level data from the U.S. Census Bureau’s Pollution Abatement Costs and Expenditures (PACE) survey to estimate a county-level index of environmental compliance costs (ECC). County-level variation is found to explain 11-18 times more of the variation in ECC than state-level variation alone, and the range of ECC within a state is often large. At least 34% of U.S. counties have ECC that are statistically different from their states’. Results suggest that important spatial variation is lost in state-level studies of environmental regulation.