USS Shiloh was a single-turreted, twin-screw monitor that was slated to enter service with the United States Navy. The contract for her construction was awarded on 24 June 1863 to George C. Bestor of Peoria, Illinois. Her keel was laid down later that year at the yard of Charles W. McCordat of St. Louis, Missouri. However, while Shiloh was still under construction, USS Chimo, one of the first of the Casco-class monitors to be launched, was found to be unseaworthy.