At the start of the American Civil War, both the North and the South had to rely on individual states to supply the armed forces with men and supplies. In the case of Ohio, Governor William Dennison turned to the Ohio militia to provide the federal government with necessary troops. The Ohio militia system had been in decline since the end of the War of 1812. With Great Britain's departure from Ohio and the declining threat from Native Americans, Ohio's citizens and their government had felt little need to strongly this system for the state's defense.
In April 1861, following President Abraham Lincoln's call for seventy-five thousand volunteers to end the South's rebellion, Dennison dispatched George McClellan and Jacob Cox to the state arsenal in Columbus to investigate the guns and other supplies that Ohio had on hand to help equip the militia units. The two men discovered a few crates of rusted smoothbore muskets, mildewed harness for horses, and some six-pound cannons that could not be fired. Despite the lack of equipment, Dennison encouraged Ohio communities to revive the militia system and to form units that they would send to Columbus, the state capital.
While the state militia system had deteriorated, numerous communities had maintained units. These units existed primarily to march in parades and to provide young men with something to do in their spare time. Among these units were the Portsmouth Guards. This unit traveled quickly from Portsmouth to Columbus, answering the governor's call. It became Company G of the First Ohio Volunteer Infantry Regiment. This unit served as part of the first two Ohio infantry regiments organized for the war. Governor Dennison dispatched these regiments to Washington, DC, to protect the nation's capital, on April 19, 1861. This was just four days after President Lincoln's call for volunteers.
- Official Roster of the Soldiers of the State of Ohio in the War of Rebellion, 1861-1866. Akron, OH: The Werner Company, 1893.
- Dee, Christine, ed. Ohio's War: The Civil War in Documents. Athens: Ohio University Press, 2007.
- Leeke, Richard. A Hundred Days to Richmond: Ohio's "Hundred Days" Men in the Civil War. Bloomington: Indiana University Press, 1999.
- Reid, Whitelaw. Ohio in the War: Her Statesmen, Generals and Soldiers. Cincinnati, OH: Clarke, 1895.
- Roseboom, Eugene H. The Civil War Era: 1850-1873. Columbus: Ohio State Archaeological and Historical Society, 1944.