A past president of Western Writers of America, Coldsmith wrote more than 40 books, as well as hundreds of newspaper and magazine articles.
In addition to his career as a writer, Coldsmith was a medical doctor, serving as a family practitioner in Emporia, Kansas, until 1988, when he chose to concentrate on writing.
His role as a combat medic in the Pacific Theater of World War II led him to Japan, where he was among the first occupying troops.
He was assigned to provide medical care for Japanese war criminals, including Hideki Tōjō, the prime minister.
After graduation, he worked as a YMCA youth director in Topeka, where he helped to achieve the first interracial public swimming pool in the state.
[citation needed] Coldsmith's fictional tribe in the Spanish Bit series appears to be a synthesis of cultural traditions of the Kansa, Lakota, Kiowa, Cheyenne, Arapaho, Blackfeet, and others.