This is the Thoroughbred Miniatures 1/600 USS Carondolet, a City-class ironclad that gained fame fighting in numerous river battles in the Western Theater of the American Civil War.
One of these ships that had been sunk (the USS Cairo) has been recovered and restored, and is now a museum ship in Vicksburg, Mississippi.
The Thoroughbred ACW ship kits are excellent and offer a huge selection of subjects that can't be found anywhere else. The kits are designed for wargaming but are detailed enough to make pleasing models as well..