After the American Civil War, he moved to Kansas City, Missouri, where he resumed his legal practice and was elected a judge before his death and burial in St. Louis.

Cowen's ancestors had moved from northern Ireland to Pennsylvania early in the 18th century, and by the American Revolutionary War were attempting to settle in the Shenandoah and Clinch River valleys.

Beginning in 1857, Preston County voters elected Cowen as one of two men to represent them (part-time) in the Virginia House of Delegates.

Reassigned on June 5, 1863, as the ACS was disbanded, Cowan then applied to become 3rd auditor in the post office on December 23, 1863, and to become a clerk in the Treasury Department on April 9, 1864.

[8] After the war, Cowan moved his family (and sister-in-law Mary Cresap) to Kansas City, Missouri, where he practiced law together with former CSA Major Blake L. Woodson (b.