Cooper began his literary activities as a writer of short stories in the 1920s under the pseudonym Matt Cooper, selling a few; in the following decade he took three correspondence courses in writing via Columbia University, where his professors suggested his style was more suited to the writing of a novel. His mother died in 1939, and his father followed her in 1940; Cooper took possession of the family home after their deaths and remained there for the rest of his life, accompanied only by the longtime family servant, Bertha Lee Walton. He converted the attic into a writing space, and spent much of his time there; it remains today as he left it after his death. Cooper offered the house to the USO during World War II, and hosted many servicemen there through the duration of the war.