This castle is situated eight miles north-by-west of Dublin, near the village of St. Margaret’s, off the Ashbourne road.

It consists of a splendidly preserved keep about 80 feet high, flanked by four square towers which rise above the roof at each corner. One of these contains a winding stair leading to the battlements, at the top of which a flight of ten steps gives egress to the summit of the watch tower.

The other three towers have little rooms opening off the different storeys.

The ground floor, which was most likely a kitchen, is a large vaulted apartment into which a door has been quarried in later years.

The first floor was once a fine wainscotted room, the walls of which were yet hung with family pictures when D’Alton visited it in 1838.

A flight of wooden stairs connects this apartment with the ground.

The two upper storeys had wooden floors, and the building is still covered by a good slated roof, which is evidently a modern addition. So too are the large square windows, some of which are glazed and others protected by wire netting. The doorways are Gothic.

In the south-west tower is the prison with no entrance except through a hole in the roof by which captives and their food were let down.

Tradition states an underground passage connects the castle with St. Margaret’s Church, as well as having many hidden vaults.

Beside the keep is the ruined chapel with an arched doorway, which has been used as a cowshed. At the side towards the castle is a low built-up archway over which is a slab carved with the symbols of the crucifixion, and having under it the inscription:—“J.P.M.D.S., 1573,” which is supposed to mean Johannes Plunket Miles de Dun-Soghly, 1573.

There seems to be no record of the building of the castle.

In 1288-89 it is noted that the rent paid for Dunsoghly by Geoffrey Brun was 74s. and fivepence. Nearly two hundred years later (1422) the King granted to Henry Stanyhurst the custody of all the messuages which had belonged to John Finglas to hold rent free during the minority of the heir. Two years later Roger Finglas is forgiven his arrears of Crown rent out of the lands and tenants of Dunsoghly and Oughtermay.

Soon after this the land seems to have passed to Sir Roland Plunkett, the younger son of Sir Christopher Plunkett, Baron of Killem, and Lord Deputy of Ireland, 1432, this family being a branch of the Fingall family.

In 1446 Sir Rowland Plunkett, of Dunsoghly Castle, was appointed Chief Justice of the King’s Bench, and later his son, Sir Thomas Plunkett, became Chief Justice of Common Pleas.

The Crown leased, in 1547, to John Plunkett, of Dunsoghly, gent., all the tithes in Dunsoghly and Oughtermay, in the Parish of St. Margaret of Dowanor, part of the possessions of the Chancellor of the late Cathedral of St. Patrick, at a rent of five marks. He was also to provide a chaplain for the church of Dowanor.

This John Plunkett was grandson to Sir Thomas, and also received knighthood. He was made Chief Justice of the Queen’s Bench in 1559. He died twenty-three years later, seized of the manors of Dunsoghly and Oughtermay.

Sir John built the private chapel belonging to the castle, and also the chantry of St. Margaret’s.

In 1590 Christopher Plunkett, of Dunsoghly, is included in the list of the English Pale; and twenty years later he surrendered Dunsoghly to the King, who re-granted it to him with additional lands on account of his own and his family’s service to the Crown.

Colonel Richard Plunkett, of Dunsoghly, was an active supporter of the Lords of the Pale in 1641, and a reward of £400 was offered for his head by the Lords Justices and Council.

In 1657 the Down Survey says that the “chiefest places in the Barony of Coolock are Malahide and Dunsoghly.” “There is in Dunsoghly a good castle, and a house adjoining it (James Plunkett).”

The House of Commons granted Sir Henry Tichbourne £2,000 in lieu of his wardship of Nicholas Plunkett, of Dunsoghly, in 1666. This Nicholas was succeeded by his son, at whose death the property was divided between his three daughters, and the castle is still in possession of their descendants.

The fortress is said to have been bombarded in Cromwell’s time from a mound near, which is now occupied by a dwelling-house, and a long crack made in the south wall by the cannon is still visible.

The castle was inhabited up to the middle of the eighteenth century.