Born on January 18, 1904 in St. Ignatius, Montana on the Flathead Indian Reservation, William D'Arcy McNickle was a novelist, author, employee of the Bureau of Indian Affairs, director of American Indian Development, Inc., community organizer, activist, professor of anthropology, historian, and program director of the Newberry Library Center for the History of the American Indian.

Born to a French Cree (Métis) mother, Philomene Parenteau, and an Irish father, William James McNickle, McNickle was the youngest child, and had two older sisters, Ruth Elizabeth and Florence Lea. McNickle's mother applied for membership into the Confederated Salish and Kootenai Tribes (known as the Flathead) and she and her children were adopted and received a land allotment under the 1887 Dawes Act. His parents divorced in 1914 and for a time McNickle went by the name of his stepfather, Dahlberg.

McNickle attended mission and government schools for Indian children in Montana and in Oregon, and attended the University of Montana from 1921-1925. In 1925 McNickle sold his land allotment and left for Europe, attending Oxford University (1925-1926) and the University of Grenoble (1931). He eventually went to work in New York and also was briefly at Columbia University in 1933. Although he never finished a degree, McNickle received an honorary Sc.D from the University of Colorado in 1966.

Eventually McNickle went to Washington, D.C. to work for the Bureau of Indian Affairs under John Collier. He worked under this "Indian New Deal" from 1936 to 1952 as an administrative assistant, a field representative for the commissioner, an assistant to the commissioner, and eventually the director of tribal relations. In 1952 he took up the directorship of the newly established American Indian Development, Incorporated, which was run out of the University of Colorado, Boulder. McNickle arranged workshops for Indian students who would arrive from across the country. Eventually the focus of the organization turned to the Navajo community of Crownpoint, New Mexico. In 1966 McNickle was invited to a professorship at the newly established University of Saskatchewan, Regina campus where he was to head and create an anthropology department. After officially retiring to Albuquerque, New Mexico in 1971, McNickle went to Chicago in 1972 to help create the Newberry Library's Center for the History of the American Indian. In 1984, the center was named after him in honor of his life and his work, making it one of two organizations named after McNickle (the second is library at the Salish-Kootenai Community College on the Flathead Reservation).

McNickle is the author of three novels: The Surrounded (1936), Runner in the Sun: A Story of Indian Maize (1954), and Wind From an Enemy Sky (1978). His non-fiction work includes They Came Here First: The Epic of the American Indian (1949), Indians and Other Americans (1959 and 1970, with Howard E. Fey), Indian Tribes of the United States: Ethnic and Cultural Survival (1962, revised in 1973 as Native American Tribalism), and Indian Man: A Life of Oliver La Farge (1971). McNickle also wrote many articles including the entry for "Indians, North America" in the 1951 Encyclopedia Britannica and books reviews for American Anthropologist. He wrote short stories and poetry too, and was published in many popular magazines including Esquire, Common Ground, the Chicago Tribune Magazine supplement, and Frontier and Midland. These stories as well as unpublished ones are included in The Hawk is Hungry and Other Stories, edited by Birgit Hans (1992).

In addition to his paid positions and his writing, McNickle worked for several other organizations. He chaired the steering committee of the 1961 American Indian Chicago Conference and was the primary author of the conference's "Declaration of Indian Purpose." He was a founding member of the National Congress of America Indians, a fellow of the American Anthropological Association, and a member of the executive committee of the Society for American Archaeology (1972-1973).

Like his mother, McNickle was married three times: first, to Joran Jacobine Birkeland from 1926-1938, second to Roma Kaye Haufman from 1939-1967, and finally to his AID co-worker, sociologist Viola Gertrude Pfrommer, from 1969-1977. McNickle had two daughters, Antoinette Marie Parenteau McNickle (with Joran) and Kathleen D'Arcy McNickle (with Roma). He died suddenly of a heart attack in October 1977.