Prior to the Industrial Revolution and the founding of Brynmawr, a settlement called Gwaun Helygen (meaning 'marsh of the willows') sat on a small area of moorland on the border between the counties of Monmouthshire and Brecknockshire.

In 1952, Jim Forrester of Enfield Cables Ltd opened a factory in the town, which was eventually acquired by the Dunlop Rubber Company.

Operating under the brand name of Dunlop Semtex Ltd, the factory produced flooring for the health and education sectors up until its closure in 1981.

The town council has its offices at the Community Centre on Orchard Street and holds its meetings at Brynmawr Institute on Market Square.

[6] A Byrnmawr local board district was established in 1851 covering parts of the two Brecknockshire parishes of Llanelly and Llangattock.

The former Market Hall is now a cinema and theatre presenting films and productions from the local amateur operatic society.

The business community offers many traditional, family-orientated and independently run shops, such as Tutta Bella, Durbans Shoe repairs, Perfectday Bridal, Pebbles and Welch Designs and many more.

Parc Nant y Waun is a nature reserve incorporating 22 hectares (54 acres) of grassland, mires and reservoirs which was officially opened in 2007.

From November 2016 and throughout early 2017, the Market Hall Cinema had been closed after Blaenau Gwent Council conducted a series of asbestos tests in the building.

[citation needed] Notable people include professional wrestlers Adrian Street and Flash Morgan Webster, singer-songwriters Huw and Tony Williams and indie pop singer-songwriter Marina Diamandis, known professionally as MARINA.,[19][20] T. Rowley Jones was President of Welsh Rugby Union, 1977/78.