The 1st Ohio Cavalry Regiment was organized at Camp Chase in Columbus, Ohio August 17-October 30, 1861, and mustered in for a three-year enlistment under the command of Colonel Owen P. Ransom.

The regiment was attached to 1st Division, Army of the Ohio, to October 1862.

(Companies F, I, K, L, and M attached to 5th Division, Army of the Ohio, May to October 1862.)

Zahm's 2nd Brigade, Cavalry Division, Army of the Ohio, to November 1862.

(Companies F, I, K, L, and M attached to II Corps, Army of the Ohio, to November 1862.)

2nd Brigade, Cavalry Division, Army of the Cumberland, to January 1863.

2nd Brigade, 1st Cavalry Division, Army of the Cumberland, to March 1863.

2nd Brigade, 2nd Cavalry Division, Army of the Cumberland, to October 1864.

2nd Brigade, 4th Division, Wilson's Cavalry Corps, to May 1865.

1st Brigade, 4th Division, Wilson's Cavalry Corps, and Department of Georgia, to September 1865.

The 1st Ohio Cavalry mustered out of service on September 13, 1865.

Company B was at Headquarters of Gen. Mitchel in Kentucky October to December 1861.

Osborn's and Wolf Creeks, near Blackland, June 4 (Companies E, I, and M).

Guard duty along Memphis & Charleston Railroad until August.

Passage of Cumberland Mountains and Tennessee River, and Chickamauga Campaign August 16-September 22.

Reconnaissance from Winston's Gap to Broomtown Valley September 5.

Cotton Port Ford, Tennessee River, September 30.

Raid on East Tennessee & Georgia Railroad November 24–27.

Tunnel Hill, Buzzard's Roost Gap and Rocky Faced Ridge February 23–25.

Ordered to Gravelly Springs, Ala., December 28, and duty there until March 1865.

Companies A and C were the first to organize and were thus ordered to western Virginia September 17, 1861.

Attached to Army of Occupation, western Virginia, to October 1861.

Cheat Mountain District, western Virginia, to January 1862.

Shields' 2nd Division, Banks' V Corps, and Department of the Shenandoah, to May 1862.

Cavalry, Shields' Division, Department of the Rappahannock, to June 1862.

Headquarters II Corps, Army of Virginia, to September 1862.

Price's Cavalry Brigade, Military District of Washington, D.C., to March 1863.

2nd Brigade, Stahel's Cavalry Division, XXII Corps, Department of Washington, to June 1863.

Headquarters 3rd Division, Cavalry Corps, Army of the Potomac, to December 1863.

In Defenses of Washington, D.C., until January 1864, when the two companies rejoined the regiment.