Objective To investigate the relationship between the percent uninsured in a county and expenditures associated with the typical emergency department visit. Data Sources The Medical Expenditure Panel Survey linked to county‐level data from the American Community Survey, the Healthcare Cost and Utilization Project, and the Area Health Resources Files. Study Design We use a nationally representative sample of emergency department visits that took place between 2009 and 2013 to estimate the association between the percent uninsured in counties and the amount paid for a typical visit. Final estimates come from a diagnosis‐level fixed‐effects model, with additional controls for a wide variety of visit, individual, and county characteristics. Principal Findings Among those with private insurance, we find that an increase of 1 percentage point in the county uninsurance rate is associated with a $20 increase in the mean emergency department payment. No such association is observed among visits covered by other insurance types. Conclusions Results provide tentative evidence that the costs associated with high uninsurance rates spill over to those with insurance, but future research needs to replicate these findings with longitudinal data and methods before drawing causal conclusions. Recent data on changes in area uninsurance rates following the ACA's insurance expansions and subsequent changes in emergency department expenditures afford a valuable opportunity to do this.