Born in North Dakota, Montgomery studied at the Western State College of Colorado. He served in the United States Air Corps from 1917 to 1918. He served as a judge in Gunnison County, Colorado from 1932 to 1937, and became a freelance writer in 1938. While still at school, he began writing stories about the wild animals that lived around his family's farm. He went on to write books about aviation and the people, landscapes and animals of the American West, particularly horses.During his career, he worked as a script writer for Walt Disney Studios. In all, he authored over 100 books.