Ystrad Tywi
Carmarthenshire has its early roots in the region formerly known as "Ystrad Tywi" ("Vale of [the river] Tywi") and part of the Kingdom of Deheubarth during the High Middle Ages, with the court at Dinefwr. After the Normans had subjugated England they tried to subdue Wales. Carmarthenshire was disputed between the Normans and the Welsh lords and many of the castles built around this time, first of wood and then stone, changed hands several times. Following the Conquest of Wales by Edward I, the region was reorganized by the Statute of Rhuddlan in 1284 into Carmarthenshire. Edward I made Carmarthen the capital of this new county, establishing his courts of chancery and his exchequer there, and holding the Court of Great Sessions in Wales in the town.