USS Elk, a 162-ton side-wheel "Tinclad" river gunboat, was built in 1863 at Cincinnati, Ohio, for commercial use. Purchased by the Navy in December 1863 under the name Countess, she was converted to a gunboat, renamed and placed in commission in May 1864. Elk was assigned to the West Gulf Blockading Squadron and served in the Lower Mississippi River and Gulf shore areas during the remainder of the Civil War. She was sold in August 1865. Subsequently reverting to the name Countess, she operated as a civilian steamer until 1868, when she was sunk.