Writing in 1682, the antiquarian Sir Henry Piers noted that the wheel at what was known as the Moate Mill was 'of the least wheel that ever I saw, which with buckets and all was not eight foot in diameter', a span of barely 2.4 metres. That detail lodges in the mind. The mill no longer stands, its site now occupied by the offices of Westmeath County Council on the banks of the River Brosna, but the documentary record it left behind is unusually full for a structure of its kind.

The Moate Mill sat in the southern quarter of medieval Mullingar, just downstream from a fording point on the Brosna and to the south-east of an Anglo-Norman motte castle, the kind of earthen mound on which a timber tower would once have stood. The pairing of mill and motte in this tight cluster of landmarks was typical of Anglo-Norman settlement planning, where economic and military infrastructure tended to concentrate around the same defensible points. By the 17th century the mill was in the hands of Thomas Petit of Irishtown, who received a formal patent grant in 1612 for 'the Moate Mill on the S side of Mollingar'. A 1641 survey describes the surrounding landscape with some precision, placing a tan house and a garden to the north and the river leading east toward the mill. By 1667, under the Acts of Settlement and Explanation that reshaped Irish landholding after the Cromwellian wars, the property had passed to Sir Arthur Forbes, described in his grant confirmation as 'Mount Mill with a parcell of pasture belonging to it'. When Piers wrote his account fifteen years later, the original over-shaft mill, in which water fell onto the top of the wheel, had already been converted to a breast mill, where water strikes the wheel roughly at its mid-point. He also noted two further mills on the same stretch of the Brosna, suggesting the river was working hard in a relatively short reach. A map drawn by Richards in 1691 captures the mill in its landscape, showing it on the south bank with the motte visible to the north. Beneath the medieval structure, there may be an even older layer: archaeologists have raised the possibility that the site was originally occupied by an early Christian horizontal watermill, a simpler technology in which a flat wheel was turned directly by the current without any gearing.