Freestanding emergency departments (EDs), which offer emergency medical care at sites separate from hospitals, are a rapidly growing alternative to traditional hospital-based EDs. We evaluated state regulations of freestanding EDs and describe their effect on the EDs’ location, staffing, and services. As of December 2015, thirty-two states collectively had 400 freestanding EDs. Twenty-one states had regulations that allowed freestanding EDs, and twenty-nine states did not have regulations that applied specifically to such EDs (one state had hospital regulations that precluded them). State policies regarding freestanding EDs varied widely, with no standard requirements for location, staffing patterns, or clinical capabilities. States requiring freestanding EDs to have a certificate of need had fewer of such EDs per capita than states without such a requirement. For patients to better understand the capabilities and costs of freestanding EDs and to be able to choose the most appropriate site of emergency care, consistent state regulation of freestanding EDs is needed.