Neolithic and Bronze Age remains are still visible within the village boundaries. The sandstone monolith Carreg-y-Llech sits on the hillside of Carreg-y-Llech Farm and is thought to be the remains of either a megalithic tomb or simply a standing stone. This stone dates back to the Neolithic period c.4500 – c.2500 BC.
Bronze Age (c.2500 – c.600 BC) tumuli or burial places are also found on the surrounding high ground; these include Bryn Tirion, Cae Boncyn, Pen-y-Stryt and Pentre.
Offa’s Dyke – the earthworks generally attributed to Offa, King of Mercia (757 – 796) – also runs along the Llanfynydd Road (the A5101). The Dyke was constructed to mark the boundary between England and Wales and runs from Sedbury in Gloucestershire to Prestatyn. 800 metres of the Dyke were traced in Treuddyn in the 1925 survey by Sir Cyril Fox.
It is believed that Llywelyn ap Gruffydd, Prince of Wales stayed in Treuddyn in 1275 during a period when he was trying to negotiate with Edward I to recognise his claim to power in Wales in return for him paying homage to the new King, Edward I. Edward I summoned Llywelyn ap Gruffydd and travelled to Chester, Llywelyn ap Gruffydd travelled to Treuddyn prior to a planned audience at Gresford but both parties returned home without meeting. This is documented in Llywelyn ap Gruffydd’s letter to Pope Gregory X requesting assistance and advice in the situation.
Over time the spelling of the village name has varied since written records were kept. The present spelling of Treuddyn was adopted by the authorities after a local campaign in approximately 1938.
Acknowledgement to sources Canon Ellis Davies : Prehistoric and Roman Remains of Flintshire, Dewi Roberts, Ken Ll. Gruffydd, Ken Jones