Frpm history.navy.mil site.
The CSS Nansemond was a 166-ton, twin-screw gunboat built at Norfolk, Virginia. It was commissioned shortly before Norfolk fell to the Union forces and was taken up the James River where it spent the rest of its career defending Richmond. It mounted two cannons, one fore and one aft.
In June-October, 1864, it took part in engagements at Trent's Reach, Dutch Gap and Fort Harrison.
It was burned 3 April 1865, to prevent capture and block the James River.
A LEGO model of it has been built and there is a scale model at Hampton Roads Naval Museum.