[4] Merionethshire was a maritime county, bounded to the north by Caernarfonshire, to the east by Denbighshire, to the south by Montgomeryshire and Cardiganshire, and to the west by Cardigan Bay.

The coastline consisted alternately of cliffs and stretches of sand and the area generally was the most mountainous in Wales; a large part of the Snowdonia National Park had been within its boundaries.

The highest point (county top) was Aran Fawddwy near the village of Dinas Mawddwy at 905 m (2,970 ft), which is also the southernmost mountain in Great Britain to exceed an altitude of 900 metres.

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.

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).

In 1245, Gruffydd's half-brother, Dafydd, launched an attack against his uncle - King Henry III - eventually resulting in the loss of the Perfeddwlad.

[5][6][7] 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.