Injury is a major public health problem generating substantial morbidity, mortality, and economic burden on society. The majority of seriously injured persons are initially evaluated and cared for by prehospital providers, however the effect of emergency medical services (EMS) systems, EMS clinical care, and EMS interventions on trauma patient outcomes is largely unknown. Outcome-based information to guide future EMS care has been hampered by the lack of comprehensive, standardized, multi-center prehospital data resources that include meaningful patient outcomes. In this paper, we describe the background, design, development, implementation, content, and potential uses of the first North American comprehensive epidemiologic prehospital data registry for injured persons. This data registry samples patients from 264 EMS agencies transporting to 287 acute care hospitals in both the United States and Canada.