The manor of Dowth first appears in historical records in 1234 under Ralph de Picheford’s ownership, when it comprised five ploughlands with a garden, dovecote and 132 acres of demesne. By the late thirteenth century, the estate had passed to the Netterville family, who would maintain their grip on it for over 600 years. Luke Netterville received confirmation of his possession in 1409, and the family’s fortunes rose considerably when Nicholas Netterville was created the first Viscount Netterville in 1622.

The castle itself is a formidable three-storey tower house featuring a stair tower at its northeast corner and defensive base-batter walls. Entry was originally gained through a flat-arched doorway in a projecting tower on the south wall, where fragments of an old bawn wall still extend southward. Inside, the ground floor boasts an east-west vault showing traces of wicker-centring, complete with corbels that once supported a loft, whilst the western wall houses a fireplace and oven. The first floor contains some remarkably preserved medieval features, including a fireplace in the west wall and an ornately punch-dressed doorway leading to a garderobe in the northeast tower, which features two beautifully decorated trefoil ventilators; clear indicators of the castle’s former grandeur.

By 1640, according to the Civil Survey, Sir John Netterville’s manor had grown to encompass 442 acres and included not just the stone house but also stables, outhouses, a church, farmhouse, malthouse, bawn, corn mill and tuck mill. The estate survived through various political upheavals of the seventeenth and eighteenth centuries, but its fortunes changed dramatically when the last Viscount Netterville bequeathed the castle and 60 acres to charity. The property was subsequently transformed into the Netterville Institute, with a seven-bay, two-storey house with attic space added to the east side to provide accommodation for widows and orphans; a charitable purpose that gave the ancient stronghold new life in the Victorian era, though the second floor was entirely rebuilt during this period.