Before the Civil War, nursing was performed by untrained nurses and female religious groups. After the outbreak of the Civil war, more women went out of the family and engaged in nursing service in military hospitals. Nursing in America transferred from religious charity activities and sporadic simple work into an indispensable profession and was developed. In the Civil War, excellent nurses saved soldiers' lives, reduced casualties and were gradually recognized by soldiers, doctors and the society. On the other hand, untrained nurses' lack of ability was exposed. The contradiction made nurses controversial and people began to consider what nursing was. Thus professional training for nurses was necessary, which caused the development of nursing education. This promoted the development of nursing education and professionalization of nursing.