The town of Castleblayney originated in the Tudor conquest of Gaelic Ulster in the Nine Years' War of 1594–1603. 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. Sir Edward was later created The 1st Baron Blayney, in July 1621. 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. The small town 'founded' by Sir Edward Blayney in 1611 or 1612 is recorded as being called "Castleblayney" at least as early as 1663.