The Canonicus-class monitor was a class of nine monitors built for the Union Navy during the American Civil War. They saw service in the Civil War and the Spanish–American War, although two of them were never commissioned.
They were basically improved s, modified in accordance with war experience. The four ships not commissioned during the war were built on the Ohio River, three at Cincinnati, and Manayunk as far up as South Pittsburgh.
The hull lines were improved and designed speed is given as 13kn but there was no hope of getting near this. The 5x side armour was backed by two iron stringers NaNabbr=onNaNabbr=on deep and 6abbr=onNaNabbr=on thick for 70feet from the bows, but 4abbr=onNaNabbr=on elsewhere, and the armour lower edge was 3×. The turret, of 21abbr=onNaNabbr=on internal diameter, had 10× plates as did the pilot house above, and the funnel base was also armored. The turret skirt was protected by a 5abbr=onNaNabbr=on thick and 15abbr=onNaNabbr=on high ring fixed to the turret, and as in other later monitors the 15 in guns were longer than in the Passaic class and fired with their muzzles outside the turret.
Tecumseh was sunk during the Battle of Mobile Bay by a mine. Canonicus, the last survivor, was decommissioned 31 years before being sold. Catawba and Oneota were both sold to Peru, on 2 April 1868, without ever entering service in the US Navy. Renamed by the Peruvian Navy as Atahualpa and Manco Capac respectively, they participated in the War of the Pacific, which lasted from 1879 to 1883.
| align=center | Ship | Builder | Namesake | Renamed | Laid down | Launched | Commissioned or completed(*) |
|---|---|---|---|---|---|---|---|
| Snowden & Mason, Pittsburgh, Pennsylvania | Manayunk, Philadelphia | Manayunk, 1862; Ajax, 15 June 1869 | 1862 | 18 December 1864 | 27 September 1865* | ||
| Harrison Loring, Boston, Massachusetts | Canonicus | Scylla, 15 June 1869; Canonicus, 10 August 1869 | 1862 | 1 August 1863 | 16 April 1864 | ||
| Alexander Swift & Company, Cincinnati, Ohio | Catawba River | bought by the Peruvian Navy in 1867; Atahualpa | 1862 | 13 April 1864 | 10 June 1865* | ||
| Secor & Co., Jersey City, New Jersey | Lake Mahopac | Castor, 15 June 1869; Mahopac, 10 August 1869 | 1862 | 17 May 1864 | 22 September 1864 | ||
| Perine, Secor & Co., Jersey City, New Jersey | Manhattan Indians | Neptune, 15 June 1869; Manhattan, 10 August 1869 | 1862 | 14 October 1863 | 6 June 1864 | ||
| Alexander Swift & Company, Cincinnati, Ohio | Oneota Tribe of the Sioux Indians | bought by the Peruvian Navy in 1867; Manco Cápac | 1862 | 21 May 1864 | 10 June 1865* | ||
| Harlan & Hollingsworth, Wilmington, Delaware | Saugus, Massachusetts | Centaur, 15 June 1869; Saugus, 10 August 1869 | 1862 | 8 February 1864 | 27 August 1864 | ||
| Charles Secor & Co., Jersey City, New Jersey | Tecumseh | Not Applicable | 1862 | 12 September 1863 | 19 April 1864 | ||
| Miles Greenwood, Cincinnati, Ohio | Wyandotte Tribe | Tippecanoe, 1869; Wyandotte, 10 August 1869 | 22 September 1862 | 22 December 1864 | 15 February 1866* |