Wentlooge, or Gwynllwg as it was called, was a kingdom within early Wales and later became a medieval Norman lordship.
Named after Gwynllyw, its 5th or 6th century ruler, it consisted of the coastal plain stretching between the Rhymney and Usk rivers, together with the hills to the north. It was traditionally regarded as part of the kingdom of Glamorgan (Morgannwg), rather than that of Gwent which extended only as far westwards as the River Usk. However, under the Laws in Wales Acts of 1535-42, the Wentlooge Hundred became included with those situated to the east, to form the new county of Monmouthshire, subsequently Gwent (1974), and now Newport (1996).
During the Roman occupation of Wales the largely marsh landscape was drained by digging ditches known as reens. The reens and remaining long thin field patterns are still evident today and are reminders of this earlier occupation. However the centuries that followed saw the gradual collapse of the sea walls and the reversion of most of the area to tidal saltmarsh.
Re-colonization of the Gwent levels in the 11th and 12th centuries was made possible by an improving climate and falling sea levels with a new sea wall constructed prior to 1126. Two churches were founded in the area during the time of the Normans, St Bridgets (first mentioned 1230 AD) in St Brides and St Peters (founded 1142 AD) in Peterstone, the latter being part of the Augustinian founded Monasterium Sancti Petri de Mora (St Peter's in the Moor).
The Black Death which caused social and economic collapse throughout Wales led to the deterioration of both churches. However, the revival period that followed enabled them to be considerably added to/rebuilt in the new Perpendicular style of the 15th century. Both churches were restored once again following the Great Flood of 1607 and again in late Victorian times.
The historian Leyland (1540s) notes that the coast between Peterstone and St Brides became a haven and medieval port served by various wharfs along a sea wall with gouts, one of which remains today.
The area has subsequently remained a tranquil rural backwater between Cardiff and Newport to the present day.