But the street plan quietly gives it away. The burgage plots, those long narrow strips of land that medieval landlords parcelled out to attract settlers, are still legible along either side of the Dunshaughlin Road and running south from Main Street toward the Broad Meadow River. The motte, a raised earthen mound on which a timber fortification would have stood, sits near the river's edge, and somewhere close to a Georgian manor house built around 1780 there was once a moated manorial site, long since abandoned even by the fourteenth century. The name itself carries the earliest clue to the place's age: it likely derives from the Irish meaning 'north', though an older reading of 'fort of Thó' hints at a pre-Norman rath that may lie folded into the base of that same motte.

The Anglo-Norman foothold here began after 1171, when Hugh de Lacy was granted Meath following the invasion. He gave the churches of Dunshaughlin and Ratoath to St Thomas' Augustinian abbey in Dublin before 1183, an arrangement that held until the abbey's suppression in 1540. On Hugh's death in 1186, Meath passed to his son Walter, who granted the baronies of Morgallion and Ratoath to his brother Hugh before 1198. It was this younger Hugh who probably raised the motte and bailey, and who may have issued a charter to the town around 1200; he went on to become the first Earl of Ulster in 1205. The manor then spent much of the thirteenth century being forfeited and restored, seized by the crown in 1210, returned in 1215, seized again in 1224, and restored once more in 1227, at which point the town was granted the right to hold a fair lasting thirteen days. By 1283 the manor had passed through several more hands, including a Welsh baron named Sir Roger de Clifford, who sold it to Queen Eleanor, wife of Edward I. Eleanor promptly granted it to Richard de Burgh, Earl of Ulster, known as the Red Earl, and it remained in de Burgh hands into the following century. A 1333 inquisition found the manor site already reduced to a half-acre surrounded by a square ditch, with no buildings standing.

By 1641 there were 21 proprietors recorded in Ratoath townland, though only four actually lived there, while 82 tenements depended on them. The town still had a portreeve and a sergeant, a working corn mill on the river, and a Monday market for provisions and linen. Despite a recorded population of just 166 around 1659, it retained its status as an incorporated borough, returning two members to the Irish Parliament right up to its dissolution in 1800. Beneath the modern surface, archaeology has kept turning up evidence of the medieval layout: a ditch, a roadway, a cistern, property boundaries, and pits found during utility work near the Catholic church and along the Kentstown road, none of it fully excavated, all of it suggesting that the town's medieval skeleton is still largely in place, just out of sight.