During the Civil War, residents of the eastern and Cumberland River sections of present-day Clay County, then part of Jackson and Overton Counties, were usually Confederate sympathizers, while those in the western section supported the Union, and men from the area enlisted in both armies. Oliver P. Hamilton organized one of the first local Confederate regiments in December 1862 and was elected major, later lieutenant colonel, of Hamilton’s Tennessee Cavalry Battalion, a partisan ranger band headquartered at Celina. His men patrolled the Tennessee-Kentucky line, enforced the conscript law, and guarded army stock and supplies between Celina and Gainsborough. As the war progressed, they skirmished frequently with Federal cavalrymen based in Kentucky. Early in June 1862, one hundred eighty of Hamilton’s men attacked a detachment of the 9th Pennsylvania Cavalry and killed its commander, but the Federals pursued them back to Celina, where Hamilton’s men scattered into the hills to evade capture. On April 19, 1863, Union Col. Felix W. Graham’s 5th Indiana Cavalry attacked Hamilton’s command at Celina, routed his forces, destroyed their camp and commissary supplies, and shelled the town. A little more than a month later, the Federals again routed Hamilton’s men at Kettle Creek. Union troops captured Hamilton at Celina in March 1864 and charged him with being a guerrilla, and while he was being transported to Lexington, Kentucky, for trail, his guards killed him under unknown circumstances.