This castle is in better preservation than other ruined castles in the county, which is doubtless due to the care taken of it by the Colthurst family since it came into their possession. Externally the castle appears as a rectangular tower or keep, whose base measures 42 feet north to south, and 32 feet east to west, with a rectangular flanking tower or fore building projecting from the east wall at its north end, of dimensions 17 feet north to south, and 10 feet from the east to its junction with the wall of the keep. Within the tower there are the two lowest floors, still more or less complete, and capable of being utilised and, above these, traces of two higher floors, making four in all, in addition to the basement of the castle. On the summit the castle has a ridged roof of slate, placed there by the late Mr Joseph Colthurst, for the preservation of the building.
The Castle of Carrignamuck was erected by Cormac Mac Teige MacCarthy (known as “Cormac Laidir”), Lord of Muskerry (1448-1494) – the same person who built Blarney and Kilcrea Castles, from each of which Carrignamuck is about eight miles distant. It was the custom for the Lords of Countries to place some relative in each of the outlying castles within the Lordship, who was there as his Lieutenant, and headed the “Rising Out” from the district under his charge when the Lord called out his muster. The Public Records show that while the Lord of Muskerry held Blarney as his residence, his tanist (successor presumptive) was always posted at Carrignamuck, and had a manor and demesne there, which thus followed the fortunes of the superior Lord. Cormac Laidir’s own brother, Eoghan, was stationed at Carrignamuck as tanist. Unfortunately, some quarrel arose at this castle between the two brothers, in the course of which Cormac received a wound from which he died. By reason of this murder of his brother, Eoghan’s claims as tanist were set aside, and he was debarred from succession.
The custom of the tanist residing at Carrignamuck continued during many generations. On the death of Sir Cormac MacTeige, in 1583, his next brother Callaghan succeeded as Lord of Muskerry; but at the end of the year he made over the Lordship to his nephew, Cormac MacDermod, the next in succession by tanistry, but retained his residency at Carrignamuck, where he remained as his nephew’s Lieutenant. He continued to keep the lands and manors permanently, and became the founder of the branch called the MacCarthy’s of Carrignamuck. His son Cormac inherited the estate, but forfeited it in 1641.
The castle was besieged and captured by the Cromwellian troops about 1650. The besiegers placed their cannon on a low hill – there are still traces of the shelter trench – at the opposite side of the Dripsey river, and made a breach in the east face of the castle in the outer of the double walls on that side, still noticeable, though afterwards built up.
The castle, town and lands of Carrignamuck were put up to sale at Chichester House Dublin on 6th November 1702, and were purchased by George Rogers Esq of Cork. Some years afterwards they passed into the possession of the Colthurst family.