USS Umpqua, a single-turreted, twin-screw monitor, was laid down in March 1863, before the official order had been placed, at Brownsville, Pennsylvania, by Snowden & Mason; launched on 21 December 1865; and completed on 7 May 1866.

These warships sacrificed armor plate for a shallow draft and were fitted with a ballast compartment designed to lower them in the water during battle to reduce the target they provided enemy guns.

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

It was discovered that Simers 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.

As a result, the Navy Department ordered on 24 June 1864 that Umpqua's deck be raised to provide sufficient freeboard.