The three-years 3rd Ohio Infantry Regiment was organized at Camp Dennison on June 12, 1861. After a few days of training and drilling, it moved to Grafton, Virginia (now West Virginia) and then on to Clarksburg on June 20–25, where it was attached to the 1st Brigade, Army of Occupation, West Virginia, until September. The regiment saw action in the West Virginia Campaign, capturing the Confederate-held town of Beverly on July 12. They remained on duty in western Virginia through the balance of the year, fighting in several small skirmishes and battles, including the battles of Rich Mountain and Cheat Mountain.