The lands here have been in the Plunket family for over 600 years, ever since Sir Christopher Plunket married Joan Cussack in 1401, bringing both Killeen and Dunsany into the family’s possession. Before this union, the barony had passed through various hands; Hugh de Lacy granted it to Adam de Feipo in 1172, and at some point the Cussack family took control, though the exact details of these early transfers remain murky. When the Plunkets divided their inheritance, the eldest son John took Killeen and his line eventually became the Earls of Fingal, whilst Dunsany went to the second son Christopher, who became the first Baron Dunsany.

The castle you see today is largely the result of Georgian and Victorian remodelling, but somewhere within its walls may lurk remnants of a medieval stronghold. The current structure consists of two tall blocks, each sporting a pair of square corner towers, connected by a hall range that creates a three-sided courtyard. In the 1780s, the 13th Lord Dunsany undertook major renovations, filling in the old courtyard to create a grand staircase hall and installing pointed Gothic windows that gave the castle its current character. Further changes came around 1840, adding another layer to this architectural palimpsest.

By 1641, Patrick Plunket, the ninth Baron Dunsany, had become a substantial landowner, controlling not just the 240 acres of Dunsany parish but also extensive holdings in Kentstown and Oldcastle, totalling over 1,000 acres across County Meath. The square corner towers visible today might preserve elements of an earlier tower house, though centuries of alterations have thoroughly disguised whatever medieval fortification once stood here. What remains certain is that this site has been continuously occupied and modified by the same family for centuries, making it a remarkable example of aristocratic continuity in Irish history.