Somewhere along the River Brosna, on the eastern bank just north of Kilbeggan in the low-lying midlands of south Westmeath, a corn mill appears on the first edition six-inch Ordnance Survey map of 1837. Its exact position has never been firmly established, and its origins are older and more tangled than the map alone would suggest.

The story runs back at least to 1606, when Sir Oliver Lambert received a Crown grant of the dissolved Cistercian abbey of the Blessed Virgin Mary at Kilbeggan, a house that had belonged to the territory of the MacGeoghegans. Among the properties listed in that grant was a water mill on the River Brosna, then called the Brassnagh or Brosnagh, along with eel weirs, cottages, arable land, pasture, and bog. When Lambert died and an inquisition into his estate was held in 1618, the record listed both a water mill and a fulling mill, the latter being a mill used to clean and thicken woven cloth by pounding it, powered by the same river. Whether these were two distinct structures or one mill serving two purposes is not clear. The Down Survey map of Moycashel Barony, produced between 1656 and 1659, depicts a single watermill on the eastern bank of the Brosna, a short distance north of the town, in roughly the same position where the corn mill appears on the 1837 Ordnance Survey map. The Cistercian monks who occupied the abbey before the Dissolution were frequently the originators of such industrial waterworks in their localities, and it is possible that the mill Lambert received in 1606 had monastic roots. The 1837 corn mill may have been built on that same site, or may even incorporate stonework from the earlier structure within its fabric, though no definitive evidence has settled the question either way.