USS Canonicus was a single-turret monitor built for the United States Navy during the American Civil War, the lead ship of her class. The ship spent most of her first year in service stationed up the James River, where she could support operations against Richmond and defend against a sortie by the Confederate ironclads of the James River Squadron. She engaged Confederate artillery batteries during the year and later participated in both attacks on Fort Fisher, defending the approaches to Wilmington, North Carolina, from December 1864 to January 1865. Canonicus was transferred to the South Atlantic Blockading Squadron at Charleston, South Carolina, after the capture of Fort Fisher in January, and helped to capture one blockade runner. She was sent to Havana, Cuba, to search for the Confederate ironclad and became one of the first ironclads to visit a foreign port. The ship was intermittently in commission from 1872 until she was permanently decommissioned in 1877. Canonicus was exhibited at the Jamestown Exposition of 1907, before she was sold for scrap the following year. Design The Canonicus class was an enlarged and improved version of the preceding . They were long overall, had a beam of and had a maximum draft of . Canonicus had a tonnage of 1,034 tons burthen and displaced . Her crew consisted of 100 officers and enlisted men. Canonicus was powered by a two-cylinder horizontal Ericsson vibrating-lever steam engine that drove one propeller using steam generated by two Stimers horizontal fire-tube boilers. The engine gave the ship a top speed of . She carried of coal. Canonicuss main armament consisted of two smoothbore, muzzle-loading, Dahlgren guns mounted in a single gun turret. Each gun weighed approximately . They could fire a shell up to a range of at an elevation of +7°. The exposed sides of the hull were protected by five layers of wrought iron plates, backed by wood. The armor of the gun turret and the pilot house consisted of ten layers of one-inch plates. The ship's deck was protected by armor thick. A soft iron band was fitted around the base of the turret to prevent shells and fragments from jamming the turret as had happened during the First Battle of Charleston Harbor in April 1863. The base of the funnel was protected to a height of by of armor. A "rifle screen" of armor high was installed on the top of