Brynmawr (Big Hill), was originally known as Gwaen Helygen (Marsh of the Willow). A mere village in 1800, it was a market town in the county of Brecknock and was formed into an ecclesiastical parish in 1875.

There were only a few farms and shepherd's cottages found in this area but soon when the iron works of Clydach, Blaenafon and Nantyglo arrived, this led to an increase in the population.

A pre-cursor of the NHS was started up here as early as 1851,with the establishment of the first board of health in England and Wales.