The borough was formed in 1974 as a local government district of Gwent.

When a borough is formed, it is still part of and dependent on its town.

The borough was formed from the following civil parishes and places:

The borough of Media was formed in 1850 from pieces of both townships.

The new borough was formed in 1862 following inflow of people for the local coal mines and steel mills.

The borough was formed from the civil parishes (with previous local authority):

Several more boroughs were formed from Ridgefield Township before the end of the 19th century.

The borough was formed from four farms purchased by the county, totalling only .

In 1929, the current borough was formed.

The borough was formed in 1974 and is an amalgamation of several former local government districts and parishes.