page_title: Canonicus-class monitor
hierarchical_section_title: Canonicus-class monitor
caption_attribution_description: Monitor "Mahopac" on the Appomattox River with Crow's Nest signal tower in the background, 1864. National Archives photo NWDNS-111-B-409
context_page_description: 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 Passaics, 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 13 knots but there was no hope of getting near this. The 5 in × 1 in side armour was backed by two iron stringers 6 ¹⁄₂ in deep and 6 in thick for 70 ft from the bows, but 4 in elsewhere, and the armour lower edge was 3 in × 1 in. The turret, of 21 ft internal diameter, had 10 in × 1 in plates as did the pilot house above, and the funnel base was also armoured. The turret skirt was protected by a 5 in thick and 15 in high ring fixed to the deck, 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 in Mobile Bay by a mine that exploded under her turret, and went down in 25–30 seconds.
context_section_description: 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 Passaics, 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 13 knots (24 km/h) but there was no hope of getting near this. The 5 in × 1 in (127 mm × 25 mm) side armour was backed by two iron stringers 6 ¹⁄₂ in (165 mm) deep and 6 in (152 mm) thick for 70 ft (21 m) from the bows, but 4 in (102 mm) elsewhere, and the armour lower edge was 3 in × 1 in (76 mm × 25 mm). The turret, of 21 ft (6 m) internal diameter, had 10 in × 1 in (254 mm × 25 mm) plates as did the pilot house above, and the funnel base was also armoured. The turret skirt was protected by a 5 in (127 mm) thick and 15 in (381 mm) high ring fixed to the deck, 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 in Mobile Bay by a mine that exploded under her turret, and went down in 25–30 seconds. Canonicus, the last survivor, was finally decommissioned 31 years before being sold.
caption: Mahopac on the Appomattox River, 1864.
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