USS C. P. Williams was a mortar schooner acquired by the Union Navy during the American Civil War. She was used for various purposes, but, especially for bombardment because of her large 13 in (330 mm) mortar that could fire up and over tall riverbanks.

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Firing on Fort McAllister from the right foreground are mortar schooners, including C.P. Williams, Norfolk Packet and Para.
History
United States
Name	USS C.P. Williams
Acquired	September 2, 1861 at New York City
Commissioned	January 21, 1862
Decommissioned	June 27, 1865
Fate	Sold August 10, 1865
General characteristics
Type	Mortar schooner
Displacement	210 long tons (210 t)
Length	103 ft 8 in (31.60 m)
Beam	28 ft 3 in (8.61 m)
Draft	8 ft 2 in (2.49 m)
Propulsion	Sail
Speed	10 kn (12 mph; 19 km/h)
Complement	35
Armament	1 × 13 in (330 mm) mortar, 2 × 32-pounder guns

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C. P. Williams was purchased by the Navy Department at New York City on September 2, 1861; fitted out as a mortar schooner; commissioned on January 21, 1862, Acting Master A. R. Langthorne in command; and reported to the Mortar Flotilla in the Mississippi River. From March 13-July 17, 1862, C. P. Williams cruised the lower Mississippi River, joining in the bombardments of Forts Jackson and St. Philip, Louisiana from April 18–23, and Vicksburg, Mississippi from June 27 – July 3 as well as blockading Berwick Bay.

C. P. Williams sailed north on July 17 for repairs at Baltimore, Maryland in September–October. On November 9, she joined the South Atlantic Blockading Squadron at Port Royal, South Carolina. She was engaged in the Battle of Legareville. During the remainder of the war, she patrolled the rivers and sounds of the area, fired in the bombardments of forts, covered landing parties, and engaged detachments of Confederate cavalry ashore. On June 9, 1865, C. P. Williams cleared Charleston, South Carolina, for Philadelphia, Pennsylvania, arriving on the 19th. She was decommissioned on June 27 and sold on August 10.

 This article incorporates text from the public domain Dictionary of American Naval Fighting Ships. The entry can be found here.