Hertzer was superintendent of nurses at a hospitals in
Boone, Iowa, and
Saint Paul, Minnesota, early in her career. She joined the U. S. Navy Nurse Corps in 1911. In 1912, Hertzer was transferred from the naval hospital in
Norfolk, Virginia to one at
Chelsea, Massachusetts, where she started as acting Chief Nurse and was officially promoted to Chief Nurse soon after. Hertzer was a member of the American Red Cross's Mercy Ship expedition in 1914, serving in
Budapest with
Helen Scott Hay and
Josephine Beatrice Bowman. "Serbs, Albanians, Hungarians, Croatians, Austrians, Montenegrins, and Russians began their long journey from the front on stretchers, ox-carts and hay wagons to the nearest railroad, where hospital trains brought them filthy, hungry, exhausted to us," she wrote of that work. In 1916, she was named Chief Nurse of the United States Navy Nurse Corps during World War I, stationed at American Red Cross headquarters in Washington D.C. She was the Navy Nurse Corps' liaison, to work with
Jane Delano on nurse recruitment during wartime. ==Personal life==