The Down Survey Maps of 1657 record two ruined castles in the area, along with several houses and cabins at Ballymore, Garrankiel and Clartane. Rush Hall itself was once known as Ballymoy or Ballymoymore, derived from the Gaelic Baile-Maige Móir, meaning 'townland of the large plain'. Today, only fragments remain of what was once a tower house at Rush Hall Court; the eastern wall, northeast angle and northern wall still stand, marking out a structure that measured approximately 6.1 metres east to west and 9.4 metres north to south.

Before the upheavals of the seventeenth century, these lands belonged to the McCostigin family, Gaelic landowners who held sway over Ballymoy and its surrounding territories. Their fortunes changed dramatically during the Cromwellian conquest when, in 1653, Augustine Costigin's extensive holdings were confiscated by the government. The forfeited lands, which included Ballymoye, Garrankiel, Clartane, Shangarry, Knockbrack, Gurtnapishy, Shangowny, Cargin, Clonefadda and portions of Gurtinamalagh and Clondaglasse, were granted to Major Thomas Davis. Davis quickly sold the property to Sir Charles Coote, who would later become the first Earl of Mountrath.

Despite the historical records documenting two castles in the area, no medieval fortifications appear on any edition of the Ordnance Survey six-inch maps, suggesting these structures had already fallen into complete ruin by the time of the survey. The surviving tower house ruins at Rush Hall Court serve as the only tangible reminder of the area's medieval past, standing as a testament to the McCostigins' lost domain and the dramatic shifts in land ownership that characterised seventeenth-century Ireland.