Overview
Canonicus-class monitor that served with Union forces late in the Civil War.
USS Mahopac is associated with United States and United States Navy. It belonged to Canonicus class, so the class page provides the shared design history while this page concentrates on the individual ship.
Construction and identity
The sources currently attached to USS Mahopac do not provide a complete builder and construction chronology.
The ship's documented identity includes alternate or later names Castor and USS Castor and service with United States Navy.
Service history
Mahopac operated in the James River and took part in operations against Fort Fisher; she briefly carried the name Castor in 1869.
The ship's configuration should be interpreted through the documented class and the dates attached to this individual vessel; equipment should not be assumed to have remained unchanged throughout service.
Class context: Canonicus class
The Canonicus class was a larger single-turret monitor design developed from Civil War experience with the earlier Passaic type. Nine ships were completed, mounting a pair of 15-inch Dahlgren guns in one armored turret.
As a member of Canonicus class, USS Mahopac shared the class's documented design framework and intended roles of Coastal combatant, Blockade, and Shore bombardment. Individual refits, transfers, and wartime changes belong to this ship only when separately documented.
Later service and disposition
The recorded final status is unknown.
USS Mahopac matters as an individual career within Canonicus class, allowing class-wide design history to be separated from this ship's own construction, identities, service, and fate.
Class relationship
This ship is recorded as a member of Canonicus class. Shared design history belongs on the class page; this page concentrates on the individual hull where evidence is available.
Sources and further reading
- Canonicus-class monitor ↗Wikipedia contributors · accessed 2026-09-18
- Canonicus I (Monitor) ↗Naval History and Heritage Command · accessed 2026-09-18
- Saugus I (Monitor) ↗Naval History and Heritage Command · accessed 2026-09-18
- Manhattan I (Monitor) ↗Naval History and Heritage Command · accessed 2026-09-18
- Tecumseh I (Monitor) ↗Naval History and Heritage Command · accessed 2026-09-18