[1] Castleblayney is near the border with County Armagh in Northern Ireland, and lies on the N2 road from Dublin to Derry and Letterkenny.

The town lies above the western shore of Lough Muckno, the largest lake in County Monaghan.

In 1611, the Crown granted forfeited lands in the area previously owned by the MacMahon chieftains to Sir Edward Blayney of Montgomeryshire in Wales for his service to Queen Elizabeth I.

King James I had already granted him appropriated Augustinian church land (or 'termon') at Muckno Friary on the northeastern side of the lake in the Churchill area (Mullandoy) in 1606/7.

[10][11] Muckno is also the name given to the Catholic parish (St. Mary's, Castleblayney, and St Patrick's, Oram, just three miles north-east of the town), which is part of the Diocese of Clogher.

[11] By about 1800 the then young Lord Blayney had ordered and implemented major reforms in Castleblayney, greatly improving the prosperity and appearance of the town.

[14] Educated in France and Germany, the 11th Lord Blayney is famous for his distinguished military career, eventually rising to the rank of Lieutenant-General, having served in the West Indies, South America, southern Africa and the Napoleonic Wars as commander of the 89th Foot, popularly known as 'Blayney's Bloodhounds'.

[18] Woodgate, a distinguished young architect, had first come over to Ireland in 1791 to supervise Soane's plans for Baronscourt, the new country house of John Hamilton, 1st Marquess of Abercorn, near Newtownstewart in County Tyrone.

[17] It is thought that this new 'castle' (in reality a country house), located in the townland of Onomy, was built close to the site of the original Blayney Castle, of which nothing now survives above ground.

[10][18] The house built for the 11th Lord Blayney was later, in the 1850s and early 1860s, substantially altered and enlarged for Henry Thomas Hope and his wife.

Hope gave the Georgian castle with its splendid prospect a Victorian makeover that the present prettified building retains, externally at least.

Rather like his father The 6th Duke of Newcastle-under-Lyne, Lord Francis lived very extravagantly and, despite his once vast family fortune, was declared bankrupt in 1896.

Hope Castle was leased between 1900 and 1904 to Prince Arthur, Duke of Connaught and Strathearn, a son of Queen Victoria.

[22] The Duke served during those years as the commander of British military forces in Ireland, whose official residence was the Master's House at the Royal Hospital, in Kilmainham, Dublin.

The 8th Duke of Newcastle-under-Lyne (1866–1941; previously known as Lord Francis Hope) sold his life interest in the castle and the estate in 1928.

[25] On 7 March 1976, a bomb exploded in the town's main street, outside the Three Star Inn pub, killing one and injuring 17 others.