Caermarthen, County of, a county of South Wales, having Cardigan on the N., Caermarthen Bay on the S., Brecon and Glamorgan on the E., and Pembroke on the W.; about 40 miles long by 24 broad, with an area of 947 square miles, being the largest county of Wales. The Black Mountains, with the Caermarthenshire Van of 2,600 feet high, occupy the S.E. of the county, and the rest of the county is of a varied and undulating character with beautiful valleys and glens. The chief river is the Towy, which receives the Gwili and Cothi, and falls into Caermarthen Bay, and is noted for its beautiful valley. The Taf, also flowing into Caermarthen Bay, drains the west of the county, and the Teify separates Caermarthen from Cardigan, and the lower course of the Llwchwr separates it from Glamorgan. Geologically, the north of the county is of Silurian formation, next to which succeeds a belt of old red sandstone, followed by belts of carboniferous limestone and millstone grit, while south of this the county forms part of the South Wales coal field. Except in the higher parts, the climate is mild, but the rainfall is great, and agriculture is comparatively backward, partly owing to the marshy nature of much of the soil and the defective drainage. The large valleys and the southern parts are the most fertile. The chief industry is agriculture and stock-raising; but the coal and iron and lead mines and the limestone quarries also employ a considerable number of people. The population" is mostly Welsh-speaking, and the manners and customs of the people, especially in the northern parts, are purely Welsh. Each of the two divisions sends a member to Parliament. The county is well served by railways, the main line from Bristol to Milford Haven running through it, besides branch lines in different directions. There are many Roman and British remains in Caermarthen, among them being traces of the Julian Way and two other Roman roads. The ruins of Carreg Cennin, and Dynevor castles are also interesting. The county was the scene of much of the struggle between Llewelyn and Edward I., and it was here that the celebrated Rebecca riots of 1843 first broke out.