The townlands of Calverstown (Blackhall) and Gormanstown located both about five miles south of Kilcullen though in different parishes, have sometimes been confused owing to their many different spellings. (This may be the reason why many facts connected with these estates appear to be contradictory). Calverstown was occupied by the Eustaces at a very early date when they built their Blackhall Castle south of the present village. John FitzMaurice of Blackhall was High Sheriff in 1400 and 1402, and was one of the twelve Delegates chosen in 1404 to control the defences of Kildare. He was probably the son of Sir Maurice of Ballycotelan (see Coghlanstown). In 1484 and again in 1493, a Richard Eustace of Kilgowan(just east of Calverstown) was High Sheriff.

Both Calverstown and Gormanstown were owned by the Viscounts Baltinglass, and Roland, later the 2nd Viscount, lived at the latter while his father was alive and occupying Harristown. At this time Calverstown was leased to a William Eustace, a juror in 1536. Both Calverstown (which contained “two castles prostrate”) and Gormanstown were forfeited after the Baltinglass rebellion, but Calverstown was re-granted to John (son of William of Castlemartin), with Harristown and Rochestown, and this grant was confirmed to his son Maurice in l627. (Blackhall, the southern part of the original estate, could not have been included in this grant, for it came in possession of the Wellesleys of Narragh more early in the seventeenth century. Perhaps it is the Calverton” forfeited after 1641 by Sir William Dixon, Protestant, and granted to Sir Richard Wellesley.) Sir Maurice gave or lent it (with Blackrath, two miles to the south-east) to his brother William, who lived in Dublin, but used Blackrath as a country residence. On his death in 1674, he bequeathed Calverstown to his daughter, Mary, or perhaps more probably, Sir Maurice had given it to her as a dowry on her marriage, a few years before, to Sir Richard Dixon. On his death in 1684, it passed to his son, then only ten years old, but later Colonel Robert Dixon, M.P. for Harristown from 1703 to 1713. On his death in 1725 it passed to his nephew, Robert Dixon, and thence to his sister, Elizabeth, who, had married Sir Kildare Borrowes, Bart. of Giltown, M for Harristown in 1721, but in 1747 it had to be sold to pay debts.

Nothing remains on either estate to mark the Eustace occupation, except their castle of Blackhall. This contains one of the very few Sheelah-na-gigs in the County, grotesquely carved female figures connected with belief in the Evil Eye. A stone kist containing a skeleton was found in Calverstown in 1788. The chapel of St. Mary (no doubt built by the Eustaces) was one of the five chapels annexed to Old Kilcullen in 1504.