A noted social reformer, Dix became the Union's Superintendent of Female Nurses during the Civil War. The soft spoken yet autocratic crusader had spent more than 20 years working for improved treatment of mentally ill patients and for better prison conditions. A week after the attack on Fort Sumter, Dix, at age 59, volunteered her services to the Union and received the appointment in June 1861 placing her in charge of all women nurses working in army hospitals. Serving in that position without pay through the entire war, Dix quickly molded her vaguely defined duties.

She convinced skeptical military officials, unaccustomed to female nurses, that women could perform the work acceptably, and then recruited women. Battling the prevailing stereo types-and accepting many of the common prejudices herself-Dix sought to ensure that her ranks not be inundated with flighty and marriage-minded young women by only accepting applicants who were plain looking and older than 30. In addition, Dix authorized a dress code of modest black or brown skirts and forbade hoops or jewelry.

Even with these strict and arbitrary requirements, relaxed somewhat as the war persisted, a total of over 3,000 women served as Union army nurses. Called "Dragon Dix" by some, the superintendent was stern and brusque, clashing frequently with the military bureaucracy and occasionally ignoring administrative details. Yet, army nursing care was markedly improved under her leadership.

Dix looked after the welfare of both the nurses, who labored in an often brutal environment, and the soldiers to whom they ministered, obtaining medical supplies from private sources when they were not forthcoming from the government. At the war's conclusion, Dix returned to her work on behalf of the mentally ill.