After the war, Walker became a companion of the Massachusetts Commandery of the Military Order of the Loyal Legion of the United States. Based upon his experiences in the military, Walker published two books describing the history of the Second Army Corps (1886) as well as a biography of General Winfield Scott Hancock (1884). Walker was elected Commander of the Massachusetts Commandery of the Military Order of the Loyal Legion of the United States in 1883 was also the President of the National Military Historical Association.