John Harris was commissioned in the Marine Corps on April 23, 1914. He was awarded a brevet rank of major in 1837 “for gallantry and good conduct in the war against Florida Indians, particularly in the affir of the Hatchee Lustee.” On January 7, 1859 he was appointed Colonel Commandant (6th Commandant) of the Marine Corps, at age 68 the oldest officer so appointed. He died as a Marine Corps Colonel while still filling that office on May 12, 1864.