[2] Before the English construction of the town of Caernarfon, the area had been occupied first by the Romans, who built the fort of Segontium, and later by both the Normans and the Welsh princes.

[11][nb 1] The walls of Caernarfon were built at the same time as the castle, under the overall supervision of Master James of Saint George, Edward's chief architect in North Wales.

Between 1283 and 1284, Richard the Engineer acted as James' deputy on the site; later, between 1295 and 1308, Walter of Hereford performed a similar role, and may have also been responsible for earlier work on the walls as well.

[16][nb 2] Otto de Grandson, a favourite of Edward I, was appointed as constable of Caernarfon and justiciar of North Wales, with responsibility for security in the region.

[18] In 1294, however, Madog ap Llywelyn revolted against English rule and undertook a wide campaign across North Wales, attacking the town of Caernarfon.

[20] Edward responded with military force the next year: he retook Caernarfon and ordered the town walls to be fully repaired by November 1295, at a cost of around £1,195.

[21] The town of Caernarfon did not prove a successful settlement, however; by 1298 it had only 59 burgage tenements—properties paying rent to the king—making it far less prosperous than either neighbouring Conwy or Beaumaris, and the situation did not improve during the 14th century.

[22] In 1400 Welsh prince Owain Glyndŵr rose in rebellion against English rule, but despite attempts to take Caernarfon in 1403 and 1404, the town's defences held out.

[26] During the 19th century the town of Caernarfon grew considerably, prompted by the slate trade and the construction of the Chester to Holyhead railway line.

[29] Today Caernarfon's walls are managed by the Welsh heritage organisation Cadw as a tourist attraction, although only a small part of the wall-walk is open to the public.

[38] The gatehouse contained offices for most of the period since its construction in the 13th century, first housing the royal exchequer, then Caernarfon's town hall and finally the guildhall.