The region which became Merionethshire previously constituted the
Cantrefs of
Meirionydd and
Penllyn, and the
Commote of
Ardudwy. Prior to the 10th century, Ardudwy formed part of the principality of
Dunoding, while Meirionydd and Penllyn were part of
Powys. Welsh records from the end of this period, and later, treat Dunoding as a vassal of
Gwynedd, ruled by an ancient cadet branch of the same family. Nevertheless, according to
John Edward Lloyd, Dunoding had been independent of Gwynedd, at the time of
Cadfan ap Iago (in the early 7th century), and before. The
Norman presence in England, after 1066, was the most significant factor which disrupted this pattern. In 1067, the rulers of Gwynedd and Powys invaded England, in support of
Eadric the Wild, a leader of continued Saxon resistance against the Normans. When Northern England revolted against in 1080, the Normans responded by preemptively attacking, and then occupying Wales, to prevent any further Welsh assistance to the English. In 1094, the Welsh decided to revolt, but
Hugh of Chester, the nearest Norman magnate, successfully re-captured North Wales by the end of 1098 (with Norwegian assistance).
Gruffudd ap Cynan, the heir to the principality of
Gwynedd, came to an accommodation with the Normans, who restored him to power in Gwynedd, excepting the
Perfeddwlad. Once Hugh died (in 1101), Gruffudd made further representations to King
Henry I, who in response granted Dunodin to Gruffudd, as well. Gruffudd's sons engaged in expansionist attacks on surrounding territory, taking Meirionydd from Powys in 1123, and annexing it to Gwynedd. Following the death of
Madog ap Maredudd, the powerful ruler of Powys, and the death of his immediate heir, Madog's remaining sons divided Powys between them. Penllyn was the portion which went to
Owain Brogyntyn. Owain was too weak, compared with his father, to resist Gwynedd's aggressive behaviour, and was forced to become a vassal of
Owain Gwynedd, the son of Gruffudd who now ruled Gwynedd; Penllyn, as a result, became a mere Cantref of Gwynedd. Dunoding is naturally divided in the middle, by
Tremadog Bay and the gorges and marshland of the
Glaslyn river; Ardudwy is the portion south of that divide. In the early 13th century,
Llywelyn Fawr, Owain Gwynedd's grandson, established a distinct territorial unit comprising Ardudwy and Meirionydd (which is immediately south of Ardudwy), and gave it to his own son,
Gruffydd, as an
appanage. In 1221, however, Gruffydd was stripped of these lands for ruling them too oppressively. In 1245, Gruffydd's half-brother,
Dafydd, launched an attack against his uncle - King
Henry III - eventually resulting in the loss of the
Perfeddwlad. When Gruffydd's son,
Llywelyn, allied with the enemies of
Edward I (Henry's son) and tried to recover the Perfeddwlad, Edward launched a huge invasion of Gwynedd, resulting in the death of Llywelyn in 1282. Two years later, in 1284, King Edward issued the
Statute of Rhuddlan, terminating
Gwynedd's existence as a state. The former appanage of Ardudwy-Merionydd, together with Penllyn, which had been part of Gwynedd for less than 150 years, were converted into Merionethshire (taking the name from Meirionydd). Merioneth was an important part of the
Welsh slate industry in the nineteenth and twentieth centuries, with major quarrying centres at
Blaenau Ffestiniog in the north of the county and
Corris in the south, with other large quarries at
Abergynolwyn,
Aberllefenni,
Arthog, and the
Cwm Ebol quarry at
Pennal. In 1947, ahead of his marriage to
Princess Elizabeth,
Lieutenant Philip Mountbatten was created
Earl of Merioneth, as well as
Duke of Edinburgh and
Baron Greenwich, by his father-in-law,
King George VI. ==Local government==