A little over a month later, she participated in Rear Admiral Samuel Francis du Pont's valiant but ill-fated attack on Charleston Harbor. The ironclads crossed Stono Bar and entered Charleston Harbor on 6 April, but a heavy fog stopped their advance lest they run aground attempting to negotiate the tricky channels leading to the vital Confederate port. Though dawn broke clear the next morning, an ebb tide kept the warships from getting underway until noon. Shortly after 15:00, 's guns opened on Fort Sumter, and through the afternoon Du Pont's ships stubbornly hammered at Confederate batteries while withstanding the intense and accurate converging fire of the Southern cannon.