When III Corps was abolished, Clark's battery was transferred to the Reserve Artillery in the brigade of Major John A. Tompkins. In that formation, Clark's battery served in the early battles of the Overland Campaign. By the time of the Battle of Cold Harbor, Clark's battery had been transferred to the artillery brigade of II Corps under Colonel John C. Tidball. In the Siege of Petersburg, Clark's battery remained in II Corp under Tidball and then under Colonel John G. Hazard. Clark was slightly wounded at the Second Battle of Ream's Station in 1864. Later he escorted the troops in his battery whose enlistments had expired back to Trenton, New Jersey, before returning to the Petersburg front. Back at Petersburg, Clark was in charge of the artillery on the front lines of II Corps in December 1864.