"A market town and parish, in the Union of Corwen, in the Nant Heudwy division of the hundred of Chirk, county of Denbigh, 21½ miles (SE by S) from Denbigh, 13½ (SE by S) from Ruthin, and 183 (NW) from London; comprising the two principal divisions of Glyn Traian and Llangollen Traian with Trevor Traian, each supporting its own poor by a separate assessment, and containing 4498 inhabitants. ..... The parish is very extensive, and the Vale of Llangollen is deservedly celebrated as containing, in proportion to its extent, a greater variety of interesting objects, and a more beautiful and striking combination of the milder and nobler features of pleasing and majestic scenery, than probably any other in the Principality." [A Topographical Dictionary of Wales, 1833 & 1849, Samuel Lewis]
The ancient parish of Llangollen was divided into three parts : Llangollen Traean, Trefor Traean, and Glyn Traean.
Llangollen Traean contained the townships of Bachau, Cysylltau, Llangollen Abad, Llangollen Fawr, Llangollen Fechan, Feifod, Pengwern and Rhisgog.
Trefor Traean contained the townships of Cilmediw, Dinbren, Eglwysegl, Trefor Isaf and Trefor Uchaf.
Glyn Traean contained the townships of Cilcochwyn, Crogeniddon, Crogenwladus, Erwallo, Hafodgynfor, Nantygwryd, Pennant and Talygarth.
On 15 April 1848, the whole of Glyn Traean, together with the township of Cysylltau from Llangollen Traean, went to form the new parish of Pontfadog.
Cysylltau returned to Llangollen in 1870.