From 1928 to 1948, field nurses served the Indian people of the Mission Indian Agency on every Indian reservation. Their work with the people ultimately led to the decline of morbidity and mortality among tribal people. Field nurses helped improve Indian health, but they did not do it alone. They could not have been successful without the support and cooperation of Native American leaders, families, communities, and tribes. Indian people allowed field nurses, physicians, and hospital employees into their lives. Indians helped health-care providers fight invisible enemies that were then sickening and killing their people. Indians worked in partnership with field nurses to improve the health of their people because, as tribal elders have testified, it was to their advantage to cooperate with field nurses and other health care providers. At the time, Indian people were dying of illnesses brought to Southern California by settlers, soldiers, and government policy makers. Settlers had introduced infectious diseases among the people. Indians reasoned that newcomers had knowledge about the causation and prevention of “traveling” sickness or infectious diseases that moved indiscriminately from person to person, place to place.