John H. Patterson, the fourth Patterson man to serve during the Civil War, enlisted as a Private in the 131st Ohio Volunteer Infantry on May 2, 1864. He was 19-years old. His duties included working in the Quartermasters office and performing prisoner escort duty.
The 131st OVI was mustered into service at Camp Chase, Columbus, Ohio on May 14, 1864 as an Ohio National Guard unit. The 131st was part of the Hundred Day Regiments commissioned by Ohio Governor John Brough as rear guard troops in an effort to free up veteran regiments for front-line combat duty in an all-out effort to seize Richmond, Virginia and hasten the end of the war.
The 131st left by train on May 15, 1864 for Baltimore, Maryland, where it was assigned to the Second Separate Brigade of the VIII Corps. The 131st never saw combat. Instead, it primarily served on garrison duty at Fort McHenry, Fort Marshall, and Fort Federal Hill. Detachments served at Washington, D.C., Harpers Ferry, West Virginia, Fortress Monroe, and City Point, Virginia.