Until 1974, Caernarfonshire, sometimes spelled Caernarvonshire or Carnarvonshire, was an administrative county in the north-west of Wales, later classed as one of the thirteen historic counties of Wales.

Until 1974, Denbighshire, or the County of Denbigh, was an administrative county in the north of Wales, later classed as one of the thirteen historic counties of Wales. It was a maritime county, that was bounded to the north by the Irish Sea, to the east by Flintshire, Cheshire and Shropshire, to the south by Montgomeryshire and Merionethshire, and to the west by Caernarfonshire.