By the early 17th century, this stronghold was held by Manus O’Donnell, brother to the Earl of Donegal, who joined the rebellion against English rule during the reign of James I. When English forces were dispatched to quell the uprising, they quickly dispersed Manus and his followers. During this campaign, an English officer named Captain Ralph Mansfield distinguished himself so notably that the king granted him the entire Killygordon estate. Though the original O’Donnell castle is now lost to time, marked only on old Ordnance Survey maps from 1836, the Mansfield legacy would leave its own substantial mark on the landscape.

Captain Mansfield wasted little time developing his new holdings. Granted 1,000 acres in the barony of Raphoe in 1610, he set about constructing a three;storey stone house and defensive bawn by 1619, though it initially stood unslated. By 1622, the house was complete and inhabited by his son’s wife and family. Nicholas Pynnar’s 1618/19 survey paints a picture of rapid plantation development, noting that Mansfield had already established a small village of nine houses at a strategic river crossing, described as “very commodious for the King’s service”. This new settlement represented the transformation of Gaelic Killygordon into a planted Ulster town.

The architectural legacy of the Mansfields may extend beyond their initial bawn and house. Killygordon House, situated nearly a kilometre north of the medieval castle site and 350 metres east of the village, is traditionally attributed to the family, though some sources date it to 1652. The exact relationship between these various structures remains somewhat unclear; it’s possible the medieval O’Donnell castle stood beside the river where the Ordnance Survey marked it, whilst Mansfield’s 17th;century house and bawn occupied what later became known as Killygordon Demesne. Today, these layers of history, from medieval Gaelic stronghold to plantation settlement, tell the story of Ulster’s dramatic transformation during one of Ireland’s most turbulent centuries.