In 1922 Federal funding was lost, and he left the Forest Service for private practice in land architecture and city planning as a partner in McCrary, Culley & Carhart. He sold his first book in 1928 and sold his interests in the firm to work full-time as a freelance writer in 1931. He made a living selling books, short stories and magazine articles for eight years. He then became the Colorado co-ordinator for the Federal Aid in Wildlife Restoration program, a position he held until 1943. He worked as the U.S. Office of Price Administration's information executive for the Rocky Mountain Region from 1944 to 1946. In 1946, he returned to writing. He wrote twenty-four books and over 4,000 articles. Carhart wrote historical novels, westerns, and books, stories and articles about forestry, wildlife management, and conservation. From 1960 to 1970, he served as a consultant to the Conservation Library Center At the Denver Public Library.