The first USS Mingo, a stern-wheel steamer built at California, Pennsylvania, in 1859 and used to tow coal barges, was purchased at Pittsburgh by Lt. Col. Charles Ellet for the War Department early in April 1862.
She was fitted out as a ram at Pittsburgh and headed down the Ohio River 29 April to join a fleet of rams which Ellet was organizing to counter the Confederate River Defense Fleet. This group of southern rams had been fitted out in the lower Mississippi and threatened to emulate the dreaded southern ironclad ram Virginia in routing wooden hulled Union ships. On 10 May the Confederate flotilla made a spirited attack on Union gunboats and mortar schooners at Plum Point Bend, Tennessee, sinking Cincinnati and forcing the Mound City aground. A fortnight later all but one of the rams had joined the Union flotilla above Fort Pillow ready for action. As the ram fleet and Western Flotilla prepared to attack, General Halleck's capture of Corinth, Mississippi, on 30 May cut the railway lines which supported the Confederate positions at Forts Pillow and Randolph, forcing the South to abandon these river strongholds.
The Confederacy charged its River Defense Fleet, the only remaining operational group of southern warships worthy of the name fleet, with the task of stemming the Union advance down the Mississippi. The South’s strategy called for a naval stand at Memphis, Tennessee.
On the evening of 6 June, Flag Officer Davis arrived above the city with his ironclads. Before dawn the next morning the Union ships raised their anchors and dropped downstream by their sterns. Half an hour later the Confederate rams got underway from the Memphis levee and opened fire.