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 in early September. Fort Sumter was reduced to a pile of rubble, but remained a formidable 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.
Sunk by a mine
On 15 January 1865, while participating in obstruction clearance operations in Charleston Harbor, Patapsco struck a Confederate mine and sank, with 75 lost. The ship's Executive Officer, Lieutenant William T. Sampson was one of a handful of survivors.
Additional technical data from Gardiner, Robert (1979). Conway's All the World's Fighting Ships 1860–1905. Conway Maritime Press. p. 120. ISBN0-85177-133-5.