In 1898 at the outbreak of the Spanish-American War, she organized volunteer nurses for the Daughters of the American Revolution. She was appointed Assistant Acting Surgeon General in the Army of the United States, and placed in charge of the army's nurses. She pursued the establishment of a permanent corp of army nurses, and is known as the founder of the Army Nurse Corps. She left her position in 1900, but continued with the Society of Spanish-American War Nurses. In 1904 she led a group of volunteer nurses to Japan.
She was the daughter of Prof. Simon Newcomb (1835-1909).