This, of course, is somewhat subjective, but it seems to be a tie between “Mother” Ann Bickerdyke and Mary Edwards Walker.

Born in 1817, “Mother” Ann Bickerdyke was living in Illinois when the war began. She was a member of the church of Edward Beecher, the younger brother of Harriet Beecher Stowe, and when the pastor learned there was a severe need for medical supplies at the front, some of the congregants went to Cairo, Illinois, where Ulysses Grant was then colonel of Illinois volunteers. Without holding any official position or title, “Mother” Ann commenced a revolution in the treatment of ill soldiers. A great believer in hygiene and sanitation, she brought the sick and wounded men outside, bathed them, and applied all sorts of relatively new medical knowledge to the situation. Within a year, she had become indispensable to the efficient running of the hospitals in the Cairo area. No one knows whether it was Ulysses Grant or William Sherman who first said “She ranks me,” but the expression took hold.