Unattached, District of the Border, VII Corps, Department of Arkansas, to March 1864.
The 12th Kansas Infantry mustered out at Little Rock, Arkansas, on June 3, 1865.
The regiment was assigned to duty by detachments on line between Kansas and Missouri until November 1863.
Company H was at Fort Larned until January 1864, then rejoined regiment at Fort Smith, Arkansas, also occupy Kansas City, Westport, and Hickman Mills, Kansas City, guarding trains and operating against guerrillas.
Companies B, E, and F escort train to Fort Smith, Arkansas, October 28-November 17, 1863.