The castle belonged to Sir Luke FitzGerald in 1640, who held 166 acres across Ardnamullan and the neighbouring townland of Aghnegalliah. Historical records from the Civil Survey of 1654-56 confirm that a castle stood on these lands, marking FitzGerald's prominence in the area during a turbulent period of Irish history.

The Down Survey maps from 1656-58 provide a fascinating glimpse into the castle's original appearance, depicting it as two connected two-storey towers, with at least one featuring a chimney; a clear sign of domestic comfort alongside defensive strength. This configuration, with towers linked by a connecting wing, was a common design in Irish tower houses of the period, combining the practical needs of defence with the requirements of noble residence.

Sadly, time was not kind to Ardnamullan Castle. By the 1980s, only the southwest corner of what was likely the main tower house remained standing, reaching a height of approximately four metres. This last vestige of FitzGerald's stronghold survived until May 1985, when it was demolished, erasing the final physical trace of a structure that had watched over the Meath countryside for centuries. Today, visitors to the site must rely on historical records and imagination to conjure the castle that once commanded this ridge in the barony of Moyfenrath.