Caerphilly (County), Wales, UK

Also/previously known as: Caerffili (Sir), Cymru, DU

The modern Caerphilly county borough was formed on 1st April 1996 as the merger of the Rhymney Valley district of Mid Glamorgan with the Islwyn borough of Gwent.

Prior to the local government reforms of 1st April 1974, Islwyn was part of Monmouthshire, while Rhymney Valley was split along the line of the River Rhymney between Glamorgan in the West and Monmouthshire in the East.