Turner Ashby spent the pre-Civil War years in farming and operating a mercantile business in the village of Markham. In October 1859 abolitionist John Brown raided nearby Harpers Ferry. Ashby responded by calling together a volunteer cavalry company, to which his reputation as a horseman and community leader attracted a large, enthusiastic following. The unit was not needed; but eighteen months later, at Virginia's secession, Ashby helped to plan the state's seizure of Harpers Ferry. (He had fought secession sentiment to the end before casting his lot with the Confederacy.)
He and his company became part of Colonel Angus McDonald's Seventh Virginia Cavalry Regiment. Late in the spring of 1861, with Federal forces poised on the north bank of the Potomac River, Ashby demonstrated the daring for which he became famous. The Confederate officer disguised himself as an itinerant horse-doctor and traveled as far as Chambersburg, Pennsylvania, to get information on Union troops, positions, and planned movements. On 25 June Colonel McDonald urged his promotion and called Captain Ashby "one of the best partisan leaders in the service." The next day, Ashby's younger brother Richard was on a patrol when he was ambushed by a hostile force. When Turner Ashby found the body, all indications were that Richard had been stabbed several times after he fell to the ground. Thenceforth, Turner Ashby became a grim avenger against all Yankees. In November, Ashby became colonel of the Seventh Virginia Cavalry.