Carnarvonshire, in Welsh Sir Gaernarfon, is a historic county of North Wales, wedge-shaped in outline, bounded on its north, south and west sides by the Irish Sea, separated from the Isle of Anglesey by the narrow strait of the Menai, and bordered on the east by Denbighshire and Merionethshire. Eighteenth-century surveys measured it at some forty miles long and twenty broad, containing 370,000 acres divided into seven hundreds and sixty-eight parishes, with one city, one borough and five market towns, lying within the diocese of Bangor. Its southern portion forms a long peninsula, and its interior is dominated by Snowdon, or Yr Wyddfa, measured by contemporary surveyors at 3,720 feet and already recognised as the highest mountain in Wales and England both.
The county's cold, piercing air, a consequence of its mountain lakes and high ground, made for a demanding but dramatic landscape, one that had already begun to attract early tourists by the 1770s, drawn by waterfalls such as the Rhaeadr Fawr near Snowdon and the wild scenery of the pass at Beddgelert. Slate quarrying in the mountains, though not yet the vast industry it would become in the following century, was already under way, foreshadowing Carnarvonshire's later role as the world's leading source of roofing slate.
Caernarfon Castle, begun by Edward I in 1283 as the administrative capital of his new principality and deliberately modelled, tradition holds, on the walls of Constantinople, together with the neighbouring castle at Conwy, completed the same year, formed two of the most formidable and complete medieval fortresses anywhere in Britain, monuments to the definitive conquest of native Wales. Dolbadarn Castle by Llyn Padarn, an earlier stronghold of the Welsh princes of Gwynedd, and Bangor's ancient cathedral church added further depth to a county whose castles alone place it among the most historically significant in the whole of Wales.