USS Keokuk, a 677-ton ironclad, was built at New York City. Originally named Moodna (sometimes incorrectly spelled "Woodna"), she was renamed prior to her December 1862 launching, and was commissioned in early March 1863. Keokuk arrived at Port Royal, South Carolina, later in that month to take up her duties with the South Atlantic Blockading Squadron.

On 7 April, she joined USS New Ironsides and seven monitors in an attack on Fort Sumter, centerpiece of the formidible defenses of Charleston, South Carolina. Under the fire of heavy Confederate guns for more than half an hour, Keokuk was struck by about ninety projectiles, many of which hit at or below her waterline. Her experimental armor, featuring alternating rows of wood and iron, was completely inadequate to protect her from this onslaught and she was "completely riddled". Though Keokuk was able to withdraw and anchor out of range, she sank on the morning of 8 April 1863, after about one month of commissioned service.