That uncertainty is not merely a gap in the records; it points to how thoroughly some medieval structures were absorbed back into the landscape, leaving cartographers and archaeologists working from documents rather than stonework.

The earliest surviving reference to castle ownership here comes from an inquisition of 1547, which records that the vicars choral of St. Patrick's Cathedral held one castle and twenty-two acres in the townland, the land lying in scattered parcels rather than in a single block. By the mid-seventeenth century, a clearer picture emerges from two related sources. The Civil Survey of Dublin, compiled between 1654 and 1656, mentions three castles in Saggart, and the Down Survey map of Newcastle Barony, produced as part of William Petty's ambitious mapping project of Ireland in 1657, depicts the settlement clustered around two tower houses, the typical form of late medieval fortified residence found across Ireland, compact stone structures several storeys high and built as much for status as for defence. A third structure on the same map is marked with the annotation "stump of a Castle," indicating it was already ruinous at the time of surveying. The accompanying written terrier, a descriptive record that accompanied the parish maps, confirms the picture plainly: "two Castles in repaire and one Stump of a Castle with some Thatcht Houses and Cabbins." The parish maps themselves survive in the National Library of Ireland as a set of forty-two maps with terriers, copied in 1786 to 1787 by Daniel O'Brien from Petty's originals.

Saggart today is a suburban village on the western edge of County Dublin, and no upstanding castle masonry is visible to the casual visitor. The value of the site lies not in what can be seen but in what the historical record preserves. Those with an interest in the Down Survey can consult the Trinity College Dublin copy of the Newcastle Barony map, which shows the settlement's seventeenth-century layout in reasonable detail. The question of which castle stood where, and which of the three the vicars choral of St. Patrick's once held, remains open.