Clara Barton, born in 1821, began her professional life as a teacher and then went on to become a recording clerk at the U.S. Patent Office. But for several of the women on this list, war was the catalyst that helped transform humanitarians into famous nurses, and the story is the same for Barton. She became known as America's "angel of the battlefield" during the Civil War.
After witnessing shortages of medical and camp supplies, she volunteered to lead efforts to bring these necessities to the battlefield, and soon began nursing sick and wounded soldiers there. After the war, Barton led efforts to locate missing Civil War veterans, and continued to advocate for soldiers and veterans for years. In 1881, at age 60, she founded the American Red Cross, based on the International Red Cross relief organization, and led the group until 1904.