Ellen La Motte was born in Louisville, Kentucky, the daughter of a businessman. In her late teens, after her father's business failed, she moved to Wilmington, Delaware, to live with her cousin, the wealthy industrialist Alfred I. du Pont. She was educated by governesses and attended the Arlington Institute, a private school for girls in Alexandria, Virginia. In 1898, she entered nursing school at the Johns Hopkins Hospital in Baltimore, Maryland. After graduation, she worked at Johns Hopkins, in Italy, and at St. Luke's Hospital in St. Louis, Missouri. She returned to Baltimore in 1905 to work as a tuberculosis nurse, which became her specialty. She published articles and gave talks to local, regional, and national audiences. She became the supervisor of the tuberculosis division of the Baltimore Health Department in 1910, the first woman to hold an executive position in that agency. She also campaigned for women's suffrage and in 1913 took a leave of absence from her job to report for The Baltimore Sun on the activities of militant British suffragists in London. She then went to Paris, where she wrote her first book, The Tuberculosis Nurse: Her Function and Her Qualifications. In 1915, she was engaged by Mary Borden to help establish a field hospital in World War I, making her one of the first American nurses to treat soldiers at the Front. She kept a diary describing the horrors she witnessed. On her return to the USA, she turned the diary into a book, The Backwash of War (1916), which was suppressed by the U.S. government as demoralizing and not published until 1934. After the war, she travelled in Asia with fellow nurse Emily Chadbourne, and accumulated material for six books, three of them on the problem of opium addiction, including Peking Dust (1919), Opium Monopoly (1920), and Ethics of Opium (1922). During the 1920s, she lived in England and traveled frequently to Switzerland to attend hearings at the League of Nations. She settled in Washington, D.C., in the 1930s.