Carlos Montezuma, whose Indian name was Wassaja, was a Yavapai Indian from central Arizona. He was captured by Pima Indians and sold to a photographer. He was educated in Arizona and New York City. He graduated from the University of Illinois in 1884 and attended Chicago Medical College. Carlos Montezuma served as a reservation physician working for the Indian Services (BIA). While working on reservations he encouraged Native American children to go to school. He eventually became a Yavapai advocate for Native Americans and helped organize the Society of American Indians, a national lobbying group; and published Wassaja, a monthly indictment of the Bureau of Indian Affairs.

This collection includes correspondence; manuscripts of lectures, articles, and reminiscences relating to his career and relationships with the federal government, reservations, and the Carlisle Indian School; and miscellaneous medical materials. Correspondents include officials of the Society of American Indians, American Indian Association, Progressive Indian Association, Richard H. Pratt, founder of Carlisle Indian School, as well as various relatives, friends, Native Americans, patients, and government officials.