Criccieth, United Kingdom

In the later years of his life, Llywelyn turned his attention to his successor. Welsh law stipulated that illegitimate sons had equal rights with legitimate sons; Llywelyn sought to ensure that Dafydd ap Llywelyn, his legitimate offspring, would inherit Gwynedd in place of his eldest, but illegitimate, son Gruffydd. On Llywelyn's death in 1240, Dafydd sought to secure his position. Dafydd was half English and feared that his pure Welsh half-brother would be able to gather support to overthrow him. Gruffydd was held prisoner in Criccieth Castle, until he was handed over to Henry III of England in 1241, and moved to the Tower of London.

Dafydd ap Llywelyn died in 1246, without leaving an heir, and was succeeded by Llywelyn ap Gruffudd, his nephew. Edward I had inherited the English throne in 1272, and in 1276 declared Llywelyn a rebel. By 1277, Edward's armies had captured the Isle of Anglesey, and were encamped at Deganwy; the settlement, the Treaty of Aberconwy, forced Llywelyn to acknowledge Edward as his sovereign, and stripped him of much of his territory. Dafydd ap Gruffydd, Llywelyn's younger brother, attacked the English forces at Hawarden in 1282, setting off a widespread rebellion throughout Wales; Edward responded with a further invasion of Gwynedd, during which Llywelyn was killed on the battlefield at Cilmeri.

With the final defeat of Gwynedd, Edward set about consolidating his rule in Wales. Criccieth Castle was extended and reshaped, becoming one of a ring of castles surrounding Edward's newly conquered territories. A township developed to support the garrison and a charter was granted in 1284; the charter was intended to create a plantation of English burgesses who would provide food for the soldiers from the arable land behind the Dinas and the grazings on the slopes beyond. Weekly markets were held on Thursdays and there were annual fairs on 25 April and 18 October, the evangelical feasts of Saint Mark and Saint Luke.

The new administration soon proved unpopular among the native Welsh, and in 1294, Madog ap Llywelyn led a national revolt against English rule. Criccieth was besieged for several months over the winter; 41 residents sought refuge within its walls, joining the garrison of 29 men under William de Leybourne, until supplies were brought in from Ireland the following April. The following year, the castle was again used as a prison, housing captives taken in Edward's wars against Scotland.

Three Welshmen who had settled in the borough, which was supposedly reserved for the English, were evicted in 1337, but times were about to change. Hywel ap Gruffydd was appointed constable of the castle in 1359, the first Welshman to hold the post. The following year came mayor of the town, holding the office for 20 years; in a poem of praise, Iolo Goch described him as "a puissant knight, head of a garrison guarding the land". By 1374 eight jurymen from the borough had Welsh names.

Richard II was deposed and imprisoned in 1399, and died in mysterious circumstances the following year. Opposition to the new king, Henry IV, was particularly strong in Wales and Cheshire, and in 1400 serious civil unrest broke out in Chester. Henry had already declared Owain Glyndŵr, a descendant of the Princes of Powys, a traitor, and on 16 September 1400 Owain launched a revolt. He was proclaimed Prince of Wales, and within days a number of towns in the north east of Wales had been attacked. By 1401 the whole of northern and central Wales had rallied to Owain's cause, and by 1403 villages throughout the country were rising in support. English castles and manor houses fell and were occupied by Owain's supporters. Although the garrison at Criccieth Castle had been reinforced, a French fleet in the Irish Sea stopped supplies getting through, and the castle fell in the spring of 1404. The castle was sacked; its walls were torn down; and both the castle and borough were burned. The castle was never to be reoccupied, while the town was to become a small Welsh backwater, no longer involved in affairs of state. The town was described in 1847 as follows,

It is a poor straggling place, with houses built without any regard to order, and having nothing worthy of notice save the ruins of the ancient castle, which stand on an eminence jutting into the sea. The population of Criccieth in 1841 was 811.

The town expanded in the 19th century with the coming of new transportation links. In 1807 a turnpike road was built from Tremadog to Porthdinllaen, which was intended to be the main port for traffic to Ireland; and with the construction of the Aberystwith and Welsh Coast Railway in 1868, the town began to develop as a Victorian seaside resort.