The 23rd Regiment, Ohio Volunteer Infantry (or 23rd OVI) was an infantry regiment in the Union Army during much of the American Civil War. It served in the Eastern Theater in a variety of campaigns and battles, and is remembered with a stone memorial on the Antietam National Battlefield not far from Burnside's Bridge.The regiment later became noted for its many postbellum politicians. Future Presidents Rutherford B. Hayes and William McKinley served in this unit, as did future U.S.