The Office of Emergency Preparedness envisioned ER One to be the nation’s first medical facility designed to cope with the results of large-scale catastrophes, including acts of biological or chemical terrorism. The Washington Hospital Center, already home to the capital’s largest emergency department, serving several hundred patients daily, was to host ER One. The project anticipated conditions in which patient-care spaces that normally handle a standard number of emergency patients would transition to handle thousands of severely injured, poisoned, or diseased patients. In addition to providing the fastest, most flexible care to patients, ER One was designed with the capacity to offload large numbers of patients by vehicle and helicopter. ER One was intended as a prototype that hospitals and trauma centers across the nation might emulate in order to increase their capacity to respond to large-scale calamity.