Castletown, as Ireland’s first and largest Palladian style house, is an important part of Ireland’s architectural heritage. Erected between 1722 and c.1729 for William Conolly, Speaker of the Irish House of Commons, Castletown House was designed to reflect its owner’s power and to serve as a venue for political entertaining on a large scale. In true Palladian fashion, the house consists of a central block flanked by two pavilions, connected by Ionic colonnades, with the kitchens on one side and the stables on the other. This style had originated in Italy with the sixteenth-century architect Andrea Palladio (1508–80), and had come to prominence in England in the early eighteenth century. The original interior layout of the house owed much to Baroque formality, with a central hall and saloon surrounded by four apartments on the ground floor and a gallery flanked by apartments on the piano noble (first floor).

William Conolly was born in Ballyshannon, Co. Donegal, in 1662, the son of a local innkeeper. From such humble origins, he rose to become the wealthiest and most powerful politician in Ireland. The Conolly family were presumably of Catholic Irish background, although it is likely they had converted sometime before William’s birth. He trained as an attorney in Dublin, where he practiced law in the 1680s. His career, however, only took off following the Williamite war of 1688-91.
In 1689, Catholic James II of England fled to Ireland following the ‘glorious revolution’ which swept his son-in-law William of Orange to power in Britain and Ireland. King William pursued his rival to Ireland, where decisive battles were fought at Derry, the Boyne, Aughrim and Limerick in 1690-1. Conolly proceeded to make the most of the opportunities created by the Williamite victory in Ireland. William of Orange confiscated the lands of James’s Catholic supporters and it was through dealing in these forfeited estates that Conolly established his fortune. By 1703, he had spent over £10,000, acquiring over 15,000 acres spread across seven counties. By any standards he had amassed an immense fortune in a remarkably short period of time.

Part of Conolly’s success, however, was based on the advantages of a successful marriage. In 1694, he had married Katherine Conyngham, the daughter of a Williamite hero, Sir Albert Conyngham. Like Conolly she was from Donegal. She was of higher social status and his marriage allied Conolly with many of the leading families in Ulster. In addition to her connections and strong personality, she brought a marriage portion of £2,300, which Conolly promptly invested in forfeited land. At the same time that Conolly was increasing his private wealth and status, he was emerging as an important public figure. In 1692, he was elected to the Irish Parliament for the town of Donegal. He would remain a member of the Irish House of Commons until 1729. In 1715, upon the accession of King George I, he was appointed Speaker of the House of Commons. His role was not to be impartial, but to act as the chief government representative in the Commons. His growing political influence was rewarded in 1717 when he was appointed one of three Lord Justices who would run the country in the absence of the Viceroy. At a time when Sir Robert Walpole was establishing himself as the first Prime Minister in England, Conolly was doing something similar in Ireland.

By the time of his death he owned over 100,000 acres and enjoyed an annual income of almost £17,000 a year, making him the wealthiest and the most powerful politician in Ireland. Castletown would become the symbol of his great wealth.

Following the sale of the house in 1965 and the dispersal of the contents a year later, the house was left vacant and subjected to vandalism. Lead was stripped from the roof, and windows were broken. Miraculously, the remaining fittings, including all the original chimney-pieces, remained. An inglorious end to Castletown’s proud history seemed inevitable. However, in 1967, the Hon. Desmond Guinness purchased the house and 120 acres of land to save it for posterity. Castletown became the flagship project of the Irish Georgian Society, which had been re-established by Desmond and Mariga Guinness in 1958. In 1967, it became the first house in Leinster to be opened to the public.

The restoration of Castletown began under the aegis of the Irish Georgian Society. Their first major task was to acquire furniture and paintings for the house. Many of the original furnishings had been secured for the house at the auction by Desmond Guinness 
Acquisitions as well as restoration work were funded by the generosity of private benefactors and were realized with the help of many enthusiastic volunteers. In 1979, the Castletown Foundation was established to take over the ownership and management of the house, but the upkeep of the house presented an uphill struggle. Following negotiations, the Office of Public Works (OPW) accepted the property on behalf of the State in 1994.

Starting that year, the OPW launched an extensive and ongoing conservation program at Castletown. The first phase of works included much needed external repairs to the fabric of the main block and stonework. On the exterior, the main block was covered with a protective temporary roof and the entire roof and parapet were dismantled and repaired. The second phase, completed in autumn 1998, addressed issues which affected the internal environment and included rewiring as well as the upgrading of the security and fire alarm systems. The third phase of works focused on structural issues and the repair of internal finishes in the main block. The ceiling of the Long Gallery was strengthened and the plaster-work conserved before the house reopened to the public in 1999.

Today, visitors to Castletown can enjoy a fine collection of Irish decorative arts within a setting that is famed both for its architectural significance and for the beauty of its natural environment. Great care has been taken not only in the conservation of the mansion but also in the restoration of the landscaped parklands, waterways and follies around it, which date back to the eighteenth century. An example of ongoing conservation works in the house is the Red Drawing Room with its nineteenth-century silk wall hangings. In 2016, the Pleasure Grounds stretching behind the house and to the west were restored, creating a quiet pleasurable retreat for visitors.