The site’s strategic importance dates back to at least 1154, when the fort built here by Turlough O’Conor was burnt by Muirchartach Ua Lochlainn. Originally known as Dún Iomain or Dún Imghain, the location controlled a crucial crossing point of the river, making it a coveted prize for successive waves of Norman and Gaelic lords.

The castle’s tumultuous medieval history began in earnest when Adam Staunton erected a castle here in 1232, likely an earthwork structure, which lasted barely a year before Felim O’Conor destroyed it in 1233. John de Stanford built another castle on the site in 1283, and this passed through the hands of the Berminghams before the Burkes acquired it around 1310. Under the Mac David Burkes, Dunamon became a significant power base until Aodh Mac an Abbot O’Conor captured it in 1400. The present stone structure probably dates from the fifteenth century when the Burkes rebuilt it, though they may have substantially remodelled it in the early seventeenth century, possibly taking inspiration from their nearby castle at Glinsk in County Galway.

The three storey castle visitors see today, measuring approximately 24.5 metres east to west and 15 to 25 metres north to south, bears the marks of multiple periods of construction and renovation. Its distinctive recessed central bays on the north and south sides, featuring arches over the second floor similar to Bunratty Castle in County Clare, speak to its medieval origins, whilst the rectangular windows with square hood mouldings likely date from nineteenth century renovations. After the Burkes were dispossessed in the 1650s, the castle passed through the King family to the Caulfields in 1668, who lived there until 1920 and added a western wing in 1855 along with the crenellations that crown the older structure. Now serving as a diocesan retreat centre for Elphin diocese, having been acquired by the Divine Word Missionaries in 1939, the castle’s fine nineteenth century plasterwork was carefully restored in the 1990s, ensuring this layered monument continues to tell its complex story.