Companies A and C served their first three year enlistment in the Eastern Theater detached from the rest of the regiment. They are honored by a monument at Gettysburg.

1861
August 17 Organized at Camp Chase, Ohio
September 17 Companies A and C ordered to West Virginia and attached to Attached to Army of Occupation, West Virginia
October Attached to Cheat Mountain District. West Virginia
1862
January Attached to Landers’ Division, Army Potomac
February 4 Skirmish at Bloomery Gap, Va.
March Attached to Shields’ Hatch’s Cavalry Command, Banks’ 5th Army Corps, and Dept. of the Shenandoah
March 7-15 Advance on Winchester
March 23 Battle of Winchester
April 17 Occupation of Mr. Jackson
May Attached to Cavalry, Shields’ Division, Dept. of the Rappahannock
June Attached to Headquarters 2nd Corps, Army of Virginia
August 9 Battle of Cedar Mountain
August 16-September 2 Pope’s Campaign in Northern Virginia
August 22 Catlett’s Station
August 27-28 Centreville
August 29 Groveton
August 30 Bull Run
September 1 Chantilly
September Attached to Price’s Cavalry Brigade, Military District of Washington, D.C. for duty in Defenses of Washington
1863
March Attached to 2nd Brigade, Stahel’s Cavalry Division, 22nd Army Corps, Dept. of Washington
June Attached to Headquarters, 3rd Division, Cavalry Corps, Army of the Potomac
July 1-3
Battle of Gettysburg

Company A was commanded by Captain Noah Jones, and was assigned to of the Cavalry Corps – 3rd Division HQ. Company C was commanded by Captain Samuel N. Stanford and was assigned to the Cavalry Corps – 2nd Division HQ. The two companies combined total 85 men, and suffered no losses.

From the monument on Taneytown Road at Gettysburg:

Companies A and C, First Ohio Cavalry, Headquarters Guard, 2d and 3d Divisions, Cavalry Corps. July 1,2,3, 1863. During the Battle of Gettysburg these companies furnished bearers of dispatches to different parts of the field. In the course of the campaign they several times vigorously engaged the enemy.

July 4 Monterey Gap
July 5 Emmettsburg
July 6-12 Hagerstown
July 14 Falling Waters
August 28 Hartwood Church
September 13-17 Advance from the Rappahannock to the Rapidan
October 9-22 Bristoe Campaign
November 5 Hartwood Church
November 26-December 2 Mine Run Campaign
December Attached to Defenses of Washington, D.C.
1864
January Regiment reenlisted as Veterans. Companies A & C served the remainder of the war with the rest of the regiment in the Army of the Cumberland in the Western Theater, participating in the capture of President Davis.