He read law, and commenced practice in Clarksburg, Virginia, where he remained for several years.
[2] When a volunteer regiment was called for from that state, he joined the one commanded by Colonel Jack Hays,[1][2] was chosen adjutant, and acted as such through the campaign.
[2] After the Mexican–American War, Harper married and practiced law for a time in Indianola, Texas[2] Towards the end of the American Civil War, Harper moved to Van Buren, Arkansas, residing there "perhaps for only two years" before being elected to the Arkansas Supreme Court in an 1864 election limited to voters deemed qualified by the Union government.
[3] Harper was one of three justices elected under the Civil War-era Constitution of 1864, the others being Thomas D. W. Yonley and Elisha Baxter.
[3] Of them it was written that they "were in office but a short time, and produced no great impression".