 After enrolling in Philadelphia in October 1860, Vaughn officially mustered in with the U.S. Marine Corps at the Marine Barracks in Philadelphia on October 31.During his service, he obtained the rank of sergeant and served aboard the USS "Tennessee" and USS "Mississippi".The steam-powered and 17-gun warship USS "Mississippi" was part of the U.S. Navy fleet commanded by Admiral David Farragut that battled with Confederate artillery batteries on March 14–15, 1863, shortly before and prelude to, the Union army's battle and siege of Port Hudson, Louisiana.