Civil War Period

Many Ohioans were strongly opposed to slavery. Slaves escaping across the Ohio River from Kentucky were helped by Ohio's Underground Railroad, which was active in many parts of the state. In 1855 antislavery advocates met in Columbus and drafted a political platform. They took the name Republican, a name already adopted by similar groups in other states. Ohio thus helped found the Republican party, which dominated the state's politics for many decades.

Before the Civil War proslavery forces in Cincinnati organized the Knights of the Golden Circle. When the war began, the Knights and their sympathizers came to be known as Copperheads. Newspapers in Columbus and Cincinnati supported the Copperhead movement, whose members believed in negotiation rather than war with the South.

When Confederate General John Hunt Morgan invaded southern Ohio in 1863, however, the Copperheads failed to aid him. Morgan was defeated and imprisoned in the state penitentiary, from which he escaped. In the same year C. L. Vallandigham, a Copperhead leader, was tried and banished for his Southern sympathies. From Canada he ran unsuccessfully for the Ohio governorship in 1863.