The site is separated from the old town by a stretch of the Owenbeg River, which flows northeast to southwest through this part of County Leitrim. Sir Frederick Hamilton, who received an initial grant of over 5,000 acres in 1621-22, had expanded his holdings to more than 16,000 acres by 1631. As part of his undertaking, he built this castle, which was likely completed around 1636.

The castle faced its first major test in January 1642 when Irish rebels laid siege to Manorhamilton. The rebel forces, led by figures including Brian McDonogh and Owen O’Rourke (or possibly Teige O’Conor of Sligo), set up camp at nearby Lugranboy. On 30 January, they succeeded in burning the town but failed to capture the castle itself, eventually lifting the siege on 3 April. The following year, Hamilton used the fortification as a base for raids reaching as far as Sligo and Donegal. Hamilton departed Ireland between 1643 and 1644, dying in Scotland in 1647, whilst his castle survived until 1652 when it was burnt by the Earl of Clanrickard.

Today, visitors can see the house situated within the northern section of a bawn measuring approximately 59 metres north to south and 37 metres east to west internally. The western side features a reconstructed wall, whilst remnants of the eastern wall’s northern end remain visible. The southern wall stands about 4 metres high externally, with evidence of corner towers surviving only at the southwest, where the western wall rises to three floors, and at the southeast, where tower foundations can be traced. Archaeological excavations conducted in 2006 revealed a cobbled courtyard surface within the bawn and evidence of a basement within the castle itself, though testing in the surrounding area has yet to uncover related materials.