USS Cossack (1861)

The Stone Fleet consisted of a fleet of aging ships (mostly whaleships) purchased in New Bedford and other New England ports, loaded with stone, and sailed south during the American Civil War by the Union Navy for use as blockships. They were to be deliberately sunk at the entrance of Charleston Harbor, South Carolina in the hope of obstructing blockade runners, then supplying Confederate interests. Although some sank along the way and others were sunk near Tybee Island, Georgia, to serve as breakwaters, wharves for the landing of Union troops, the majority were divided into two lesser fleets. One fleet was sunk to block the south channel off Morris Island, and the other to block the north channel near Rattlesnake Shoals off the present day Isle of Palms in what proved to be failed efforts to block access the main shipping channels into Charleston Harbor.

Various old ships, specifically purchased by the Navy for this purpose, were loaded with stone and sand, or filled with dirt, then towed to a designated spot and sunk as a hazard to all craft that passed. Twenty-four whaleships were sunk in Charleston Harbor by Captain Charles Henry Davis, beginning on 19 December 1861. A second fleet of 12 to 20 vessels was sunk in nearby Mafitt's Channel in 1862. The operation was under the direction of Samuel Francis DuPont, Flag Officer commanding the South Atlantic Blockading Squadron. Confederate general Robert E. Lee called the measure "an abortive expression of the malice and revenge" of the North.

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