There were five corps in the Union Army designated as II Corps during the American Civil War. These formations were the Army of the Cumberland II Corps commanded by Thomas L. Crittenden from October 24, 1862, to November 5, 1862, later renumbered XXI Corps; the Army of the Mississippi II corps led by William T. Sherman from January 4, 1863, to January 12, 1863, renumbered XV Corps; Army of the Ohio II Corps commanded by Thomas L. Crittenden from September 29, 1862, to October 24, 1862, transferred to Army of the Cumberland; Army of Virginia II Corps led by Nathaniel P. Banks from June 26, 1862, to September 4, 1862, and Alpheus S. Williams from September 4, 1862, to September 12, 1862, renumbered XII Corps; and the Army of the Potomac II Corps from March 13, 1862, to June 28, 1865.

Israel Bush Richardson was a United States Army officer during the Mexican–American War and American Civil War, where he was a major general in the Union Army. Nicknamed "Fighting Dick" for his prowess on the battlefield, he was mortally wounded at the Battle of Antietam near Sharpsburg, Maryland.