Born in Ohio, James Ketner was practicing law in Leavenworth, Kansas, when the civil began. On September 1, 1861, Ketner was commissioned captain of Company K, 1st Kansas Infantry. Ketner was promoted to major on June 19, 1863. Ketner mustered out with the regiment on June 17, 1864. On October 8, 1864, Ketner mustered into the 16th Kansas Cavalry as a major.
Major Ketner led the 16th Kansas Cavalry, part of Col. Thomas Moonlight's 2d Brigade, during the Battle of Westport. Ketner fought on October 19 at Lexington. Ketner's 16th Kansas Cavalry was place in the advance during the Federal pursuit following the Battle of Mine Creek. They were part of the attack at the Battle of Newtonia on October 28, 1864.
Ketner received a brevet promotion to brigadier general on March 13, 1865 and mustered out with the regiment on December 5, 1865. After the war, Ketner returned to Leavenworth and his law practice. Ketner remained active in politics serving as a delegate to Kansas State Conventions for both the National Union Party and the Democratic Party. In 1883, Kansas Governor George W. Glick appointed Ketner major general of the Kansas State Militia.
Hinton, Richard J. Rebel Invasion of Missouri and Kansas, and the Campaign of the Army of the Border against General Sterling Price, in October and November, 1864. Chicago: Church & Goodman, 1865.
Kansas Adjutant General, Report of the Adjutant General of the State of Kansas, 1861-’65, 6, 22, 57, 534.
Wilder, Annals of Kansas, 437, 707-708, 717-718, 891892, 1020, 1062, 1074.