A Gothic Revival seat on the Unshin, in the barony of Tirerrill.

Markree Castle stands on the River Unshin, just east of Collooney in Co. Sligo. It is not an Ó Dubhda castle, and the site was never part of the Ó Dubhda lordship of Uí Fiachrach Muaidhe. The land belonged for centuries to the McDonaghs, lords of Tirerrill — a branch of the MacDermots — and was granted after the Cromwellian settlement to the English soldier Edward Cooper, whose descendants remodelled the old fort into one of the largest country houses in the north-west. The Cooper family held Markree for ten generations before selling to the Corscadden hoteliers in 2015. We include Markree in this Estate Tour because it sits in the broader Sligo landscape, and because its nineteenth-century observatory gave Ireland its first — and for 160 years only — asteroid discovery. But the ground it occupies was McDonagh, not Ó Dubhda.

I. Origins — McDonagh country

The earliest castle at Markree was a medieval fort guarding a crossing of the River Unshin. It stood in the barony of Tirerrill (Tír Oirill), held by the McDonaghs, a branch of the MacDermots of Moylurg. Between Tirerrill and the Ó Dubhda country of Tír Fhiachrach lay the O’Hara lordship of Leyny; Collooney and Markree were McDonagh ground, two lordships removed from the Ó Dubhda. Nothing of the medieval fort is visible today; the present house is recorded as containing parts of earlier houses on the site (NIAH).

II. The Cooper grant

Cornet Edward Cooper came to Ireland as an officer in the Cromwellian army. Under the Restoration Act of Settlement (1662) his holdings in Co. Sligo were confirmed, and he was established at Markree by 1663. By the 1720s the Coopers were among the largest landowners in Co. Sligo, with over 40,000 acres (Irish Historic Houses).

A local tradition long attached to this Cooper the story of Máire Rua Ní Mhathúna — the “Red Mary” who, after her second husband Conor O’Brien fell in 1651, married a Cromwellian Cornet Cooper to preserve her son’s inheritance. Her Cromwellian marriage is real, but the standard authorities name her husband as John Cooper, an officer of Ireton’s army, and her castle was Lemeneagh in Co. Clare, not Markree. The story that she married Edward Cooper of Markree is still told at the castle, but it is not supported by the documentary record.

III. Francis Johnston and the Gothic Revival

In 1802 the Coopers engaged Francis Johnston (1760–1829) — the foremost Irish architect of his generation, later the architect of the General Post Office in Dublin (1814), the Chapel Royal at Dublin Castle (1807–14), and the Richmond Tower at the Royal Hospital Kilmainham — to remodel the old manor as a castellated Gothic Revival mansion. The 1802 house was built over the raised basement of the previous Cooper house. Enlargements followed later in the nineteenth century: a porte-cochère, a square battlemented tower, and a chapel on the north front were added c. 1866-70 to designs by James Maitland Wardrop, with a canted bay window to the west; an ornamental garden doorway followed in 1896 (NIAH). Inside, a carved wooden gallery surrounds the reception hall and a Victorian double staircase of oak rises beneath a heraldic stained-glass window tracing the Cooper pedigree.

IV. Markree Observatory and the discovery of Metis

In 1830 Colonel Edward Joshua Cooper, MP (1798–1863) established a private observatory in the grounds. Its principal instrument was a Cauchoix refractor with a 13.3-inch object glass, mounted in 1834 on a Grubb equatorial; for a brief period it was the largest refracting telescope in the world. The Royal Astronomical Society described it in 1851 as “the most richly furnished private observatory known.”

On 25 April 1848 Cooper’s assistant Andrew Graham identified a new minor planet; it was given the name 9 Metis. It was the first asteroid discovered from Ireland — and the only one for a hundred and sixty years, the next being found from Celbridge, Co. Kildare, in 2008. The observatory continued in operation until the death of Edward Henry Cooper, MP, in 1902; after that it was run down and its instruments dispersed.

V. Decline, hotel, Corscadden

The Cooper holdings were largely sold under the Land Acts of the late nineteenth and early twentieth centuries. Free State troops occupied the castle during the Civil War; the family returned, but in the later twentieth century the house fell into decay and stood empty for some years. Charles Cooper, tenth generation of the family to reside there, reopened Markree as a country-house hotel in 1989. In 2015 the Coopers sold the estate to the Corscadden family, Irish hoteliers; after renovation it reopened in March 2017 as the present hotel and event venue.

Two unrelated notes attach to the castle’s later history. The hymn-writer Cecil Frances Alexander stayed at Markree in 1848, the year Hymns for Little Children was published; a local tradition holds that the view from the terrace inspired “All Things Bright and Beautiful,” though the claim rests on association rather than documentation. And on 16 January 1881 a reading of −19.1 °C was recorded at Markree — still the lowest air temperature in the Irish record.

VI. The Ó Dubhda connection — an honest statement

Markree is not an Ó Dubhda castle, and the Ó Dubhda never held Tirerrill. Markree sits in Co. Sligo but east of the clan heartland; the Collooney area was McDonagh ground. The only honest connection is the shared post-Cromwellian landscape: the same Act of Settlement that confirmed Cornet Edward Cooper at Markree also ratified the dispossession of Gaelic owners across Tír Fhiachrach, including the Ó Dubhda themselves. Markree is therefore a settler-family house on Gaelic Sligo ground — but not on Ó Dubhda Gaelic ground. It is included in this Estate Tour as a neighbour, not as a cousin.

VII. Visiting

Markree operates today as a country-house hotel and exclusive-hire venue. The castle is open to hotel guests and to those attending weddings and events; there is no general-admission heritage tour. The observatory does not survive as a visitable building. Practical details — bookings, opening dates, and access — are on the hotel’s own site at markree.com.