Caerphilly (Welsh: Caerffili; [kɑːɨrˈfɪli]) is a county borough in southern Wales, straddling the ancient county boundary between Glamorgan and Monmouthshire. It is governed by Caerphilly County Borough Council.
Caerphilly County Borough is in southeast Wales and straddles the border between the historic counties of Glamorgan and Monmouthshire. It is bordered by Cardiff to the southwest, Newport to the southeast, Torfaen to the east, Blaenau Gwent to the northeast, Powys to the north, Merthyr Tydfil to the northwest and Rhondda Cynon Taf to the west.
The northern part of the borough is formed by the broad expanse of the Rhymney Valley. The Rhymney River rises in the hills in the north and flows southwards for about thirty miles, looping round to the east just to the north of Caerphilly before reaching the Bristol Channel. Some of the larger towns are Bedwas, Risca, Ystrad Mynach, Newbridge, Blackwood, Bargoed, New Tredegar and Rhymney. The valley also includes the communities of Abertysswg, Fochriw, Pontlottyn, Tir-Phil, Brithdir, New Tredegar, Aberbargoed, Rhymney and Ystrad Mynach, and the towns of Bargoed and Caerphilly.
Located on the edge of the South Wales Coalfield this area was sparsely populated with livestock husbandry being the main occupation. Farmers in their remote farmhouses on the windswept pastures might dig themselves some bucketfuls of coal for their hearth. Things began to change with the development of the iron industry, the start of the Industrial Revolution. In 1752, a 99-year lease was granted for a parcel of land in the Rhymney Valley which gave the lessees the right to mine coal and iron ore. Other such transactions followed, pitshafts were dug and the coal industry developed. By the beginning of the twentieth century, there were forty coalmines in the valley.
One of the pits sunk in the late nineteenth century was the Elliot Colliery. At its peak before World War I, it was producing over a million tons of coal a year and employing nearly three thousand people. The coal eventually became depleted and the colliery closed in 1967. Most of the site was cleared but the East Winding House survives and is now a Grade II listed building, and a museum of the coal industry in the area has been opened on the site. All the pits in the valley were closed by the end of the twentieth century; the spoil heaps were removed and the area was landscaped so that it is not now apparent that the valley ever had an industrial past.
The county borough was formed on 1 April 1996 by the merger of the Rhymney Valley district of Mid Glamorgan with the Islwyn borough of Gwent. In 2008, as a result of representations from different communities in the borough, a draft plan was put forward proposing various changes to the borders between communities.