In 1870-72, John Marius Wilson's Imperial Gazetteer of England and Wales described Y Gyffylliog like this:
GYFFYLLIOG, or CYFFYLLIOG, a parish and a subdistrict in Ruthin district, Denbigh. The parish lies on a rivulet of its own name, an affluent of the Clwyd, 5 miles W of Ruthin town and r. station; and contains the townships of Ffrithoed, Trefor, Treganol, and Trepark. Post town, Ruthin, Denbighshire. Acres, 6, 652. Real property, £2, 076. Pop., 564. Houses, 114. The property is divided among a few. The living is a p. curacy, annexed to the vicarage of Llanynys, in the diocese of St. Asaph. The church is a poor edifice.The sub-district contains also two other parishes. Acres, 18, 923. Pop., 1, 326. Houses, 281.
A Vision of Britain through Time includes a large library of local statistics for administrative units. For the best overall sense of how the area containing Y Gyffylliog has changed, please see our redistricted information for the modern district of Denbighshire. More detailed statistical data are available under Units and statistics, which includes both administrative units covering Y Gyffylliog and units named after it.
GB Historical GIS / University of Portsmouth, History of Y Gyffylliog in Denbighshire | Map and description, A Vision of Britain through Time.
Date accessed: 05th March 2015
Click here for more detailed advice on finding places within A Vision of Britain through Time, and maybe some references to other places called "Y Gyffylliog".