At the crest of a steep north-east-facing slope on a broad ridge in Co. Waterford, a single upright stone marks the point where a boundary wall changes direction. It measures roughly 0.8 metres across and stands 1.2 metres high, built into the southern face of a stone-clad sod wall. That wall, running along the county boundary between Waterford and Tipperary, had already been old for decades when Ordnance Survey cartographers recorded the stone by name in the 1840 edition of their six-inch map. They called it the Duke's Stone, and the name has stuck, anchored to a landscape most travellers never cross.

The wall also traces the outer limits of the Lismore estate, which was mapped in 1774 by the surveyor Richard Scalé. By then the estate had been in the hands of the Cavendish family for over twenty years. William Cavendish, the fourth Duke of Devonshire, acquired the Lismore lands in 1753 through his wife, Lady Charlotte Boyle, who was the heiress of the fourth Earl of Cork. The Cavendishes were one of the most powerful aristocratic families in Britain, and Lismore Castle in Co. Waterford became their Irish seat. Which particular Duke the stone was named for is not entirely clear; it may refer to the fourth Duke himself, or to one of the successors who inherited the estate after him. What seems likely is that the stone served a practical purpose, a fixed marker on the ground at a spot where the boundary line bends and where any ambiguity about ownership could have real consequences on a large managed estate.

The stone sits where the county boundary shifts course, which would have made it a useful reference point for anyone walking the bounds or settling a dispute about where Waterford ended and Tipperary began. It is incorporated into the wall rather than standing free, suggesting it was either already in place when the wall was built or was deliberately set into it to formalise the corner. Either way, it is a quietly functional object, a piece of estate administration rendered in stone and left on a windswept ridge for the better part of three centuries.