Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The 125th Illinois Volunteer Infantry was an infantry regiment in the Union Army during the American Civil War. The 125th Illinois Infantry was organized at Danville, Illinois and mustered in for three years service on September 3, 1862 under the command of Colonel Oscar Fitzalan Harmon. The regiment was attached to 36th Brigade, 11th Division, Army of the Ohio, to October 1862. 36th Brigade, 11th Division, III Corps, Army of the Ohio, to November 1862. 2nd Brigade, 4th Division, Centre, XIV Corps, Army of the Cumberland, to January 1863. 2nd Brigade, 4th Division, XIV Corps, to June 1863. 2nd Brigade, 2nd Division, Reserve Corps, Army of the Cumberland, to October 1863. 3rd Brigade. 2nd Division, XIV Corps, Army of the Cumberland and Army of Georgia, to June 1865.