Knight illustrated books and magazines, and became a frequent contributor to "National Geographic". He also wrote and illustrated several books of his own, such as "Before the Dawn of History" (Knight, 1935), "Life Through the Ages" (1946), "Animal Drawing: Anatomy and Action for Artists" (1947), and "Prehistoric Man: The Great Adventure" (1949). Additionally, Knight became a popular lecturer, describing prehistoric life to audiences across the country.