"This place, which is situated among lofty hills in a rich mineral district, in the south eastern part of the county, abounds with coal and ironstone of superior quality; and within the last few years some very extensive works have been established here, which are carried on with very great success. .... About four hundred and fifty men are constantly employed in the collieries and other works at this place."
[ A Topographical Dictionary of Wales, S. Lewis, 1834]
Treuddyn is regarded as being one of the ancient parishes of Flintshire; although, to be strictly accurate, it was a chapelry of the ancient parish of Mold until it officially became a separate parish on 27 May 1844. In practice, Treuddyn had long operated as a separate parish, although it was held jointly with Nercwys until 1832.
In many Civil Registration records, and Census returns, the name appears as "Tryddyn". This was officially changed to "Treuddyn" in 1938.