The townland of Ballyroan has given its name to the Catholic Parish of the Holy Spirit despite the fact that the parish church is located in the neighbouring townland of Old Orchard. Ballyroan townland crosses both barony and civil parish boundaries. The 6th Ordnance Survey map (1936-37) shows Ballyroan as consisting of 115 acres in the civil parish of Tallaght in the barony of Uppercross and a further 10 acres in the civil parish of Rathfarnham in the barony of Rathdown.
The fact that the townland boundary crosses the superior land divisions of parish and barony, the fact that the townland name is now used to cover a wider area than the townland itself and the present association of the townland with Rathfarnham rather than Tallaght, points to a loss of identiy of the townland. It is a townland over which and around with borders and events have moved with little regard for its boundaries.
Ballyroan is situated on the northern slopes of the foothills of the Dublin/Wicklow Mountains at a hight of 250 feet above sea level. The soil is fertile, being based on glacial till and has a moderately wide use range. Ballyroan townland is surrounded by Old Orchard, Butterfield, Knocklyon, Scholarstown and Ballyboden townlands. The modern townland of Ballyroan consists of major portions of the lands of Sancta Maria College, St. Patrick's National School, Mercy Convent, Ballyroan House and major portions of the following housing estates - Ashtown Lawn, Close and Grove, Ballyroan Heights, Elkwood, Hillside Park and Templeroan Estate (excluding the major portion of Templeroan Green and a small portion of Templeroan Court).
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