USS Patapsco, a 1335-ton Passaic class monitor built at Wilmington, Delaware, was commissioned in early January 1863. Assigned to the South Atlantic Blockading Squadron, she took part in a bombardment of Fort McAllister, on Georgia's Ogeechee River, on 3 March. On the 7th of April Patapsco joined eight other ironclads in a vigorous attack on Fort Sumter, off Charleston, South Carolina, and received 47 hits from Confederate gunfire during that day. Beginning in mid-July, she began her participation in a lengthy bombardment campaign against Charleston's defending fortifications. This led to the capture of Fort Wagner, on Morris Island, in early September. Fort Sumter was reduced to a pile of rubble, but remained a formidible opponent.

In November 1863, Patapsco tested a large obstruction-clearing explosive device that had been devised by John Ericsson. Remaining off South Carolina and Georgia during much of 1864 and into 1865, the monitor, or her boat crews, took part in a reconnaissance of the Wilmington River, Georgia, in January 1864 and helped capture or destroy enemy sailing vessels in February and November of that year. On 14 January 1865, while participating in obstruction clearance operations in Charleston Harbor, USS Patapsco struck a Confederate mine and sank, with heavy loss of life.