The 103rd Regiment, Ohio Volunteer Infantry was a three-years' infantry regiment from northeastern Ohio that served in the Union Army during the American Civil War. It participated in many of the campaigns and battles of the Army of the Ohio in the Western Theater.
On July 21, 1862, William B. Castle, as chairman of the District Military Committee in Cleveland, sent a letter to Governor David Tod, enclosing a copy of a resolution recommending that the appointment of company officers for the 103rd Regiment, Ohio Volunteer Infantry. The new regiment was to draw members from Cuyahoga County, Lorain County and Medina County.
The 103rd OVI was organized at Cleveland in August 1862 under command of Colonel John S. Casement. It was ordered to Kentucky on September 3, 1862, and attached to the 2nd Brigade, 1st Division, Army of Kentucky, Department of the Ohio. The regiment saw action in Kentucky, Georgia, Alabama and Tennessee.
The 103rd mustered out on June 12, 1865. It lost during its term of service two officers and 137 enlisted men killed and mortally wounded, and three officers and 106 enlisted men by disease, a total 248 fatalities.
In 1866, veterans formed the 103rd O.V.I. Association. They and/or their descendants have held a reunion every year since, the only U.S. organization of its kind. The association operates the 103rd Ohio Volunteer Infantry Museum in Sheffield Lake, Ohio that houses, preserves and displays historic Civil War relics which have been inherited, collected by or donated to the descendants of the members.