From Lewi’s, A Topographical Dictionary of Ireland: “CASTLE-BLAYNEY, a market and post-town, in the parish of MUCKNOE, barony of CREMORNE, county of MONAGHAN, and province of ULSTER, 11 miles (S. E. by E.) from Monaghan, and 49 (N. N. W.) from Dublin; containing 1828 inhabitants. It derives its name and origin from Sir Edward Blayney, governor of the county of Monaghan in the reign of James I., who, in consideration of the dependence of his garrison at Monaghan and Newry for a supply of provisions, which was rendered precarious by the hostility of the intervening country, received a grant of two ballybetaghs of land here, on condition of his erecting a fort between Monaghan and Newry; Castle-Blayney was accordingly erected, as a secure halting-place for the royal troops, and Sir Edward received this extensive estate, which his descendants still enjoy. The collection of habitations formed in the vicinity never, however, assumed the appearance of a town until the establishment of the linen market, and the rebuilding of the houses with stone, in the latter part of the last century, by the late noble proprietor.

It is situated on the mail coach road from Dublin to Londonderry, and comprises 341 houses; is lighted by subscription, and has a respectable appearance. It consists of three streets meeting in the market-place, which is of a triangular form; and in the centre, on an elevated spot commanding every avenue, is the market-house, a very neat and ornamental building, with a spacious room on the second story, and a neat bell turret above the roof. Near the market-house are convenient shambles. The manufacture of linen, though not so extensive as formerly, furnishes employment to many persons in the surrounding districts; and there are three tanyards in the town. The principal market is on Wednesday, when considerable quantities of yarn and flax are sold: there are also markets for corn and butter on Tuesday and Friday; and fairs for live stock are held on the first Wednesday in every month. Here is a constabulary police station; also a neat sessions’-house, in which the quarter sessions for the county are held four times in the year, and petty sessions every alternate week; and a county bridewell, which affords the necessary accommodation for the classification of prisoners.

The mansion of Castle Blayney, the seat of Lord Blayney, is closely adjoining, and is encompassed by a demesne of great extent and beauty, which includes the Lake of Mucknoe and some fine woodland scenery: it is a handsome modern edifice, built near the site of the old castle. The ruins of an ancient fortress in Cornero wood, on the shore of the lake, are also within the demesne. The parish church of Mucknoe is in the town; it is very neat, with a handsome spire, and the interior has been comfortably fitted up by Lord Blayney, who has also planted the churchyard with trees and evergreens. There are also places of worship for Roman Catholics, Presbyterians, and Wesleyan Methodists. The parochial school, situated here, has an average attendance of 35 children; and there is a school for girls, supported by Lady Blayney, with an average attendance of 70 children.