As the day of attack on Charleston approached, Keokuk and were busy laying buoys to guide Rear Admiral Samuel Francis Du Pont's ironclad flotilla, which included , seven monitors (Weehawken, Passaic, Montauk, Patapsco, Catskill, Nantucket, and Nahant), and Keokuk, into the strongly fortified Confederate harbor.
The First Battle of Charleston Harbor began at noon on April 7, but difficulties in clearing torpedoes from the path of Du Pont's ironclads slowed their progress.