The 20th Ohio Infantry Regiment was organized at Columbus, Ohio April through May 1861 in response to President Lincoln's call for 75,000 volunteers and mustered into service on May 23, 1861, under the command of Colonel Charles Whittlesey.
[1][2][3][4] The regiment was ordered to western Virginia and attached to Kelley's Command.
It participated in action at Richter June 23 and the pursuit of Garnett July 15–16.
The 20th Ohio Infantry was reorganized at Columbus August 19 through September 21, 1861, and mustered in for three years service on October 21, 1861, under the command of Colonel Charles Whittlesey.
[5][6] The regiment was attached to 3rd Brigade, 3rd Division, Army of the Tennessee, February to May 1862.
2nd Brigade, 3rd Division, Right Wing, XIII Corps, Department of the Tennessee, to December 1862.
The 20th Ohio Infantry mustered out of service at Louisville, Kentucky, on July 18, 1865.
The detailed service of the three-year 20th OVI is as follows: Moved to Camp King near Covington, Ky., and mustered in October 21.
Expedition toward Purdy and operations about Crump's Landing, Tenn., March 9–14.
Guard duty at Pittsburg Landing until June, and at Bolivar, Tenn., until September.
Grant's Central Mississippi Campaign November 2, 1862, to January 10, 1863.
Moved to Memphis, Tenn., January 26, thence to Lake Providence, La., February 22, and duty there until April.
Movement on Bruinsburg and turning Grand Gulf April 25–30.
Operations about Marietta and against Kennesaw Mountain June 10 – July 2.
Assault on Kennesaw June 27, Nickajack Creek July 2–5.