The Twentieth Wisconsin Infantry Regiment was organized and its final muster into the service of the United States completed at Camp Randall, Madison, Wisconsin August 23, 1862. The regiment left the state August 30 and joined General Herron's Brigade at Rollo, MO, September 6, and was sent on a march to southwestern Missouri, participating in the campaign then being conducted against the Confederates by the Army of the Frontier in southwestern Missouri and northwestern Arkansas. It took part in the battle of Prairie Grove, AR December 7, 1862.
The Twentieth continued in active service in southwestern Missouri until the following June, when the regiment was transferred to Vicksburg and took its place in the trenches June 15, 1863, remaining a part of the besieging forces until the surrender July 4, following. After Vicksburg, the regiment was in service on various expeditions in Mississippi and Louisiana, including one to Natchez, Port Hudson and Morganza. Later in the year, the Twentieth accompanied the Texas expedition which left New Orleans October 26, 1863, disembarking at Brazos, Santiago, TX and going on duty at or near Brownsville, TX, on the Rio Grande, where it remained until the following August. During this time it participated in many expeditions, including a two day excursion across the Rio Grande into Mexico, January 12-14, 1864. Returning to New Orleans in August, the Twentieth formed a portion of the land forces accompanying Admiral Farragut's Expedition against the Confederate forces in Mobile Harbor in August, 1864. The regiment participated with the land forces investing Ft. Morgan until the surrender of that stronghold on August 23, 1864. The 20th remained in southern Alabama and took part in the investment of Spanish Fort, March 27 to April 8, 1865, and the reduction and capture of Fort Blakely April 19, 1865.
In the latter part of June, the Twentieth was situated at Galveston, TX, where it remained and performed the usual duties of garrison service until mustered out of the service of the United States July 15, 1865. It reached Madison July 30, and was disbanded August 9, 1865.
