USS Yazoo — a single-turreted, twin-screw monitor — was laid down in March 1863, before final government approval had been given, by Merrick & Sons, Philadelphia.

Yazoo was a Casco-class monitor intended for service in the shallow bays, sounds, rivers, and inlets of the Confederacy.

These warships sacrificed armor plate for a shallow draft and were fitted with a ballast compartment designed to enable them to ride exceptionally low in the water during battle.

Though the original designs for the Casco-class monitors were drawn by John Ericsson, the final revision was created by Chief Engineer Alban C. Stimers following Rear Admiral Samuel F. Du Pont's failed bombardment of Fort Sumter in 1863.

It was discovered that Stimers had failed to compensate for the armor his revisions added to the original plan and this resulted in excessive stress on the wooden hull frames and a freeboard of only 3 inches.