(Monitor: t. 614; l. 208'9"; b. 37'; dr. 6'6"; cpl. 69; a. 2 guns)
A bay on the coast of Maine.
Casco was launched May 1864 by Atlantic Works, Boston, Mass. Prononunced unseaworthy when nearly completed, on 25 June 1864 she was ordered to be converted to a torpedo vessel, without turret or heavy guns. Casco was commissioned 4 December 1864, Acting Master C. A. Crooker in command.
After completion of additional yard work, Casco was towed to Hampton Roads in March 1865. She assisted in the removal of torpedoes in the James River which made possible the advance of naval forces to Richmond. In mid-April she was transferred to the Potomac Flotilla, with whom she served until the end of May. Casco was decommissioned 10 June 1865 at Washington Navy Yard, where she was broken up in April 1875.