Until 1974, Llanrhaeadr-ym-Mochnant was split into two civil parishes: the northern parish was in historic Denbighshire and the southern parish in historic Montgomeryshire; this reflected the division of the ancient commote in the 12th century. The divide continued between 1974 and 1996, with the former Denbighshire parish being placed in Clwyd and the former Montgomeryshire parish in Powys, each with their own community councils. In 1996, both parts of Llanrhaeadr-ym-Mochnant were united within the county of Powys, and the community councils were amalgamated in 2008.