CSS Manassas, a 387-ton ironclad ram, was originally built at Medford, Massachusetts, as the screw towboat Enoch Train. Purchased in 1861 by Captain John A. Stevenson of New Orleans, she was converted to a warship at Algiers, Louisiana. Her above-water hull was reshaped to a "turtle-back" form and covered with iron plating. She was given a pointed iron ram at the bow and carried a single gun that fired forward through a small opening. Her low profile made her a difficult target, while her armor protected her against all but the most well-directed enemy gunfire.

Placed in privateer service in September 1861, Manassas was soon taken over by the Confederate Navy and was formally purchased by the Government in December 1861. On 12 October of that year, she attacked the Federal blockading force at the Mississippi River's Head of Passes. The big steam sloop USS Richmond was rammed and seriously damaged, but survived. Manassas was also damaged, mainly by the force of her own ramming effort, but successfully withdrew and was repaired.

Continuing her employment with the Confederacy's defenses on the Lower Mississippi, Manassas played a dramatic role in the major battle that took place during the night of 24 April 1862, when U.S. Navy Flag Officer David Glasgow Farragut boldly took his squadron up the river past Confederate Forts Jackson and Saint Philip to capture New Orleans. During the action off the forts, Manassas attacked the large Union warships Pensacola, Mississippi and Brooklyn. She was able to ram the last two, though not fatally, before running aground. USS Mississippi then disabled her with withering cannon fire. Abandoned and afire, Manassas drifted downstream, exploded and sank.