The steam-powered gun turret of the Osage was at the bow and she had a deckhouse between the funnel and the sternwheel, although another was later added between the turret and the funnel. Her pilothouse was positioned above the rear deckhouse, next to the forward face of the sternwheel. The ship was long overall and had a beam of. When launched she proved to have a draft deeper than planned and she measured 523 tons burthen. Osage had four steam boilers powering a two-cylinder, western steamboat-type engine that drove the sternwheel. The ship had a maximum speed of in service and she carried of coal. Her crew numbered 100 officers and enlisted men. Osages main armament consisted of two smoothbore Dahlgren guns mounted in a single turret that had an arc of fire of 300°. Firing the guns tended to jam the turret until modifications were made to the guns' recoil system. Each gun weighed approximately. They could fire a shell up to a range of at an elevation of 15°. The turret was protected by of wrought iron while the hull had of armor. The armor plates of the deck and paddle housing were thick.
Service
Osage, named after the American Indian tribe, was laid down in mid-1862 and launched 13 January 1863 by James Eads at his Union Iron Works, Carondelet, Missouri. She was commissioned at Cairo, Illinois on 10 July 1863, with Acting Volunteer Lieutenant Joseph Pitty Couthouy in command. After completion, the ship was assigned to Rear Admiral David Porter's Mississippi Squadron and patrolled the Mississippi River against Confederate raids and ambushes. During the Red River CampaignOsage was commanded by Lieutenant Commander Thomas O. Selfridge, Jr. She supported the Union Army when it captured Fort DeRussy and captured Alexandria, Louisiana by herself on 15 March 1864 without firing a shot. She successfully defended the navy transports attacked during the Battle of Blair's Landing on 12 April, driving off the Confederate forces with heavy losses after having run aground and freed herself. After the end of the campaign in May she was assigned to patrol the Mississippi River. During that month she grounded on a sandbar near Helena, Arkansas and could not be refloated due to the rapidly falling water level even when some of her armor was removed. As the water receded Osage began to hog at the ends because only her middle was supported by the sand. This caused her longitudinal bulkheads to split and broke many rivets in her hull and on her deck. She was repaired in place before being refloated at the end of November. After being towed to Mound City for more permanent repairs, Osage was transferred to the WestGulf Blockading Squadron on 1 February 1865 for the attack on Mobile, Alabama. She participated in the Battle of Spanish Fort, defending Mobile from the east, but struck a mine in a previously swept channel and sank rapidly on 29 March. Two crewmen were killed and some others wounded. The ship was later refloated and sold at auction at New Orleans on 22 November 1867, along with three ex-Confederate ships, for $20,467.
