The 12th Ohio Infantry Regiment was organized at Camp Dennison, Cincinnati, Ohio, on May 3, 1861, for three-months service, and reorganized on June 28 for three years, under Colonel John W. Lowe, who was killed early in the war and was succeeded by Col. Carr B. White. The 12th Ohio served in western Virginia until August 1862, when it was transferred to the Army of the Potomac and participated in the battles of Second Bull Run, South Mountain and Antietam.