(ScStr: t. 370; 1. 145'7"; b. 23'9"; dr. 11'2"; cpl. 44; a. 1 30-pdr. P.r., 1 12-pdr. how.)
Trefoil, a wooden-hulled screw steamer built in 1864 by clipper ship designer Donald McKay, was purchased by the Navy on 4 February 1865 and commissioned at the Boston Navy Yard, Boston, Mass., on 1 March 1865, Acting Master Charles C. Wells in command.
Trefoil proceeded south to the Gulf of Mexico and arrived at Mobile Bay on 24 March. She served in the West Gulf Blockading Squadron under Rear Admiral Henry Knox Thatcher through the end of the Civil War, operating mainly as a dispatch boat between Pensacola and Mobile.
In July 1865, she returned north to the Boston Navy Yard where she was decommissioned on 30 August 1865. Placed in ordinary in 1866, the steamer was sold at auction on 28 May 1867 to a Mr. L. Litchfield.