This article previews selected findings of the American Association of Critical-Care Nurses History Project that is being conducted under the auspices of the Center for the Study of the History of Nursing at the University of Pennsylvania. Using methods of social history research, we reviewed pertinent literature, studied documents of institutions and organizations, and interviewed a broad array of participants. Analysis of this evidence resulted in a history of the evolution of nursing and hospital care for patients with life-threatening illnesses during the 40-year period since 1950. We explored the effects of changing public and professional ideas about the nature of critical illness, the effects of technology, and the historical dimensions of critical care nursing. Special attention was given to the events and circumstances that led to the development of AACN and the reciprocal relationships between AACN and the care of critically ill people.