D.J. O'Malley (1867-1943) was a cowboy for the N Bar N Ranch, the Montana Cattle Company's 79 Ranch, and other cattle ranches around Montana. His papers consist primarily of cowboy poetry and other writings reflecting his experiences as a cowboy; a small amount of correspondence (1887-1939); and miscellany, including a few items concerning his father Dominick O'Malley's Civil War military career.