an elevation of +15°. Ozark was chosen as the testbed for an experimental "underwater battery" that consisted of a nine-inch Dahlgren gun firing through a pipe in the side of the hull below the waterline. Cost overruns caused the project to be cancelled in January 1863 before it could be tested. The cylindrical Ericsson-style turret was armored with six layers of wrought iron plates. The forward of the hull was protected by two layers of plates that extended below the waterline. Aft of the bow section, the hull's armor consisted of two layers of plates. The ship's deck was protected by iron plates one inch thick. Construction and service The contract for Ozark, the first ship of that name in the United States Navy and named for the Ozark Tribe of the Quapaw Indians, was awarded to George C. Bestor on 14 May 1862. He subcontracted the ship's construction to Hambleton, Collier & Co. at their Mound City Marine Ways shipyard in Mound City, Illinois. Ozark was laid down in 1862 and launched on 18 February 1863. She was towed to St. Louis for fitting out and arrived there on 27 February. Ozark commissioned on 18 February 1864, with Acting Volunteer Lieutenant George W. Brown in command. She cost about $215,000. Ozark spent her entire Union Navy career serving in the Mississippi River Squadron. From 12 March to 22 May 1864, she took part in the Rear Admiral David Porter's Red River Expedition to Alexandria, Louisiana. During the retreat down the Red River, Ozark was trapped above the falls at Alexandria, along with most of the other ironclads of the Mississippi Squadron, when the river's water level unexpectedly began to fall. Two temporary dams, known as Bailey's Dam, had to be built in April–May to raise the water level high enough to allow the ironclads to proceed downstream. After the end of the campaign, Ozark was assigned to the Third District, patrolling the Mississippi River between Morganza, Louisiana and Fort Adams, Mississippi. Following the end of the war, she was decommissioned at Mound City on 24 July 1865 and was sold 29 November. The identity of her purchaser is not known, nor are her activities after her sale, but Ozark was still in service in late 1873 and based at New Orleans. Louisiana governor William Pitt Kellogg used the ship to transport 35 soldiers of the 19th Infantry Regiment and