Twenty year old Clarke ran away to America from Suffolk county, England, in 1847. After several unsuccessful business ventures he enlisted in the First U. S. Dragoons, serving from 1849 to 1854. While stationed at Jefferson Barracks, Mo., in 1850, he met and married an Irish girl, Mary McGowan. Upon his release from the army he became clerk to the quartermaster at Fort Leavenworth, later being stationed at Fort Riley. In 1860 he purchased a toll bridge over the Kansas river on the Fort Riley military reservation, and when floods carried it away in the spring of 1861 he established a ferry. On October 4, 1861, Clarke became a first lieutenant in Co. I, Sixth Kansas Mounted volunteers - later Co. F, Sixth Kansas cavalry. On October 21 he was made a captain and until his death served as assistant adjutant general to Gen. J. W. Denver. He died suddenly at Memphis, Tenn., December 10, 1862, leaving his widow with five young sons to rear. Her letters from Junction City continue the story to 1872.