At the outset of the Civil War, the cavalry of the Army of the Ohio (Michigan, Ohio, Indiana, Illinois, Pennsylvania, Kentucky, and Tennessee) was a fledgling force beginning an arduous journey that would make it the best cavalry in the world. In late 1862, most of this cavalry was transferred to the Army of the Cumberland and a second cavalry force emerged in the second Army of the Ohio.

Throughout the war, these regiments fought in some of the most important military operations of the war, including Camp Wildcat; Mill Springs; the siege of Corinth; raids into East Tennessee; the capture of Morgan during his Great Raid; and the campaigns of Middle Tennessee, Perryville, Knoxville, Atlanta, and Nashville. This is their complete history.