Osage, after being refloated and repaired, was transferred to the West Gulf Blockading Squadron in early 1865 for the campaign against Mobile, Alabama.

[1] Osage's main armament consisted of two smoothbore 11-inch (279 mm) Dahlgren guns mounted in a single turret[4] that had an arc of fire of 300°.

[4] 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 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.

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.

[8] After being towed to Mound City for more permanent repairs,[9] Osage was transferred to the West Gulf 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.