It was a sister unit to the 7th Missouri Infantry Regiment (the "Irish Seventh") and in 1864 was consolidated with a battalion of veteran volunteers of that regiment and operated as a "demi-brigade" known popularly as the "Missouri Irish Brigade".
It was often referred to as the "Shamrock Regiment" due to the large number of Irish immigrants who were enlisted in its ranks.
1st Brigade, 11th Division, Right Wing 13th Army Corps (Old), Department of the Tennessee, December 1862.
1st Brigade, 4th Division, Sherman's Yazoo Expedition, to January 1863.
13th Army Corps (New), Military Division West Mississippi, to July 1865.
Assault and capture of Fort Hindman, Arkansas Post, January 10–11.
Moved to Young's Point, La., January 17–23, and duty there till March.
Expedition to Greenville, Black Bayou and Deer Creek April 2–14.
Moved to Join army in rear of Vicksburg, Mississippi, via Richmond and Grand Gulf, May 2–14.
Assigned to garrison duty at post of Vidalia till April 1864.
Guard pontoon train at Big Black River July 3–9.
Moved to Morganza July 28–30, thence to Port Hudson, Louisiana, August 23–24.
Moved to Morganza August 28, and to mouth of White River, Ark., September 3–8.
Mustered out at Columbus, Texas, August 31, and discharged at St. Louis, Mo., September 11, 1865.