The city of St Asaph is surrounded by countryside and views of the Vale of Clwyd. It is situated close to a number of busy coastal towns such as Rhyl, Prestatyn, Abergele, Colwyn Bay and Llandudno. The historic castles of Denbigh and Rhuddlan are also nearby.
The earliest inhabitants of the vale of Elwy lived in the nearby Paleolithic site of Pontnewydd (Bontnewydd), which was excavated from 1978 by a team from the University of Wales, led by Dr Stephen Aldhouse Green. Teeth and part of a jawbone excavated in 1981 were dated to 225,000 years ago. This site is the most north-western site in Eurasia for remains of early hominids and is considered of international importance. Based on the morphology and age of the teeth, particularly the evidence of taurodontism, the teeth are believed to belong to a group of Neanderthals who hunted game in the vale of Elwy in an interglacial period.
The Cathedral has had a chequered history. In the thirteenth century, the troops of Edward I of England burnt the cathedral almost to the ground and, in 1402, Owain Glyndŵr's troops went on the rampage causing severe damage to the furnishings and fittings. Two hundred and fifty years later, during the Commonwealth the building was used to house farm animals – pigs, cattle and horses.
The Laws in Wales Act 1535 placed St Asaph in Denbighshire. However, in 1542, St Asaph was placed in Flintshire for voting purposes. Between 1 April 1974 and 1 April 1996 it was part of non-metropolitan Clwyd.
As the seat of an ancient cathedral and diocese, St Asaph was historically regarded as a city, and the 1911 Encyclopædia Britannica refers to it as a city on that basis; by the end of the 20th century the relationship between possessing a cathedral and automatic entitlement to city status had been broken, and the town was no longer regarded as a city. The town applied for restoration of city status in competitions held by the government in 2000 (for the Millennium) and 2002 (Queen's Golden Jubilee) but was unsuccessful. In 2012 it again competed for the right to become a city as part of the Queen's Diamond Jubilee celebrations. It was announced on 14 March 2012 that the application was successful and city status was to be bestowed upon St Asaph alongside Chelmsford and Perth. The status was formally granted by letters patent dated 1 June 2012.