Campbell was born Benny Campbell in Auburn, California. His mother, Mary Vierra (Vieira), was a Portuguese immigrant who had come with her mother to the U.S. at age six through Ellis Island, (according to Campbell, his maternal grandfather had entered the United States some time before.) The Vierra family settled in the large Portuguese community near Sacramento. When Mary Vierra contracted tuberculosis in her youth, she was forced to convalesce at a nearby hospital, often for months at a time during treatment. It was there that she met an American Indian patient Albert Campbell, who was at the hospital for alcoholism treatment. Albert Campbell was of predominantly Northern Cheyenne descent but, according to Nighthorse Campbell biographer Herman Viola, Albert Campbell spent much of his youth in Crow Agency boarding school and may have had some Pueblo Indian and Apache Indian blood in his background as well. The couple married in 1929, and Campbell was born in 1933.