He had published a biography of Robert Lucas by the time he earned his Ph.D., and soon thereafter published biographies of John Chambers and George Wallace Jones.
He served with the Intelligence Section of the American Expeditionary Force during World War I, then returned to lecture in history at the University of Iowa from 1920 to 1922.
He stayed at UCLA until a severe illness in 1936 forced him to take time off from teaching.
He made a partial recovery and returned to teaching in early 1937, but died two years later.
Parish edited a number of collections and journals during his career, and founded the Pacific Historical Review.