Marshall grew up in Eugene, Oregon, where he attended the University of Oregon from 1913 to 1916. He served in the U.S. Army with the rank of second lieutenant. He married Agnes Sharp Flythe; they had two children, Edison and Nancy. In 1926, they moved to Augusta, Georgia.
His novel Benjamin Blake was adapted into a film in 1942, Son of Fury, starring Tyrone Power, as was The Vikings, starring Kirk Douglas, in 1958.