Cassius Clay Pettijohn was born around 1842 in Ohio to Lewis and Eleanor Pettijohn. His father was a Wesleyan minister who owned $200 of real estate and $300 of personal property by 1860. The family lived in Troy, Ohio, until the 1850s, when they moved to Sardinia, Ohio. By 1860, he was working as a teacher.
He enlisted in the Union army on August 12, 1862, and he mustered in as a private in Company E of the 50th Ohio Infantry. The regiment took part in the Battle of Perryville and the Atlanta campaign. He eventually earned a promotion to sergeant. His father fell ill in the 1860s, and he used his wages to help support the family. His mother later testified that he was “our only support. He was farming rented land before he went to help put down the rebellion, and after he entered the Service of his country, he sent home twelve dollars per month…which was spent for the benefit of the family, paying house rents, doctor’s bills etc.” He was wounded near Dallas, Georgia, on May 31, 1864, and he died on June 4, 1864.