Five decades ago, hospitals staffed their emergency rooms with rotating community physicians or unsupervised hospital staff. Ambulance service was frequently provided by a local funeral home. Beginning in the late 1960s and accelerating thereafter, emergency care swiftly evolved into its current form. Today, modern emergency departments not only are capable of providing around-the-clock lifesaving care in individual emergencies and disasters. They also conduct timely diagnostic workups, provide access to after-hours acute care, and serve as the "safety net of the safety net" for millions of low-income and uninsured patients. But the field's success has led to a new set of challenges. To overcome them, emergency care must become more integrated, regionalized, prevention oriented, and innovative.