"A parish in the Union of Ruthin, partly within the limits of the borough of Denbigh, and partly in the hundred of Isaled, county of Denbigh; 3 miles (SE) from Denbigh, containing 2066 inhabitants. This very extensive parish is fourteen miles in length, and on an average three miles in breadth: it abounds with limestone, of which there are several quarries in various parts, great quantities being procured to be burnt for manure in several kilns here, and for building." [A Topographical Dictionary of Wales, 1833 & 1849, Samuel Lewis]
The ancient parish comprised the townships of Cader, Meifod, Segroit Ucha, Segroit Isa, Cliccedig, Prion, Llanllech and Llwyn, Trefydd Bychain, and Llewesog; with a total area of 16,308 acres.
During the nineteenth century, more than half the area of the ancient parish was transferred to the parishes of Prion (6000 acres), Nantglyn (2007 acres), Cyffylliog (1800 acres), and Denbigh (300 acres); so that by 1913, the area of the parish of Llanrhaeadr yng Nghinmeirch had been reduced to 6200 acres.