USS Lancaster was a sidewheel civilian steamer tow boat built in 1855 at Cincinnati. It was originally named Lancaster Number 3 then Kosciusko. In March through May 1862, she was purchased and converted to a ram by Colonel Charles Ellet Jr. to serve during the American Civil War as part of the United States Ram Fleet and the Mississippi Marine Brigade.
On 10 May the Confederate ram flotilla, known as the River Defense Fleet, attacked Union gunboats and mortar schooners at Plum Point Bend, Tennessee, sinking USS Cincinnati and forcing USS 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 Henry Wager 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 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 Charles Henry 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, beginning the Battle of Memphis.
At this point Colonel Ellet ordered his rams to steam through the line of Flag Officer Davis’ slower ironclads and run down the Confederate steamers. His flagship USS Queen of the West headed straight for CSS Colonel Lovell, the leading southern ram. A moment before the two ships crashed, one of Colonel Lovell‘s engines failed causing her to veer. The Union ram’s reinforced prow smashed into Colonel Lovell‘s side ripping a fatal hole in her side. When Queen of the West pulled free from Lovell she ran aground on the Arkansas shore. Meanwhile, Union ram USS Monarch crashed into foundering Colonel Lovell with a second blow which sent her to the river bottom with all but five of her crew. By then Davis’ ironclads had steamed within easy range of the southern ships and began to score with the effective fire. In the ensuing close action, the Confederate River Defense Fleet was destroyed; all of its ships, except CSS General Earl Van Dorn, were either captured, sunk, or grounded to avoid capture. Memphis surrendered to Flag Officer Davis.