Grain processing was not incidental to power; it was part of its fabric, and the right to operate a mill was bound up with the control of land, labour, and local trade.

The historical record here is brief but pointed. In 1621, Hugh Mageoghegan of Castletown was formally recorded as holding the manor of Castleton, in the barony of Kinalleen, a grant that encompassed sixty acres, a castle, a fair, and a water-mill. The Mageoghegans were a Gaelic dynasty with deep roots in County Westmeath, and by the early seventeenth century they were navigating the pressures of plantation-era land arrangements. To be "seised in fee" meant to hold land outright by freehold tenure, a legal formulation from English property law that was being applied with increasing insistence across Ireland during the reign of James I. The fact that the mill appears alongside the castle and the fair in a single patent roll entry suggests it was understood as a working part of the manor's economic life rather than an afterthought. Water-mills of this period were typically set on a reliable millrace diverted from a local river or stream, and their operation would have served the surrounding agricultural community while also generating income for the lord.