The Amman Iron Company was formed in 1847 when Mr Llewellyns bought existing works at Gwter Fawr from Mr Jones, Brynbrain, and built 2 blast furnaces there. These were part of the expansion of the iron industry in the western coalfield following the hot blast experiment at Ynyscedwyn which enabled smelting with anthracite for the first time (in 1836). These developments later led to the massive expansion of the iron industry in the USA, where anthracite was the principal coal available.

Llewellyns built company houses in Hall St and elsewhere, and the works expanded with a forge added 1851, replaced in 1861. The name of Gwter Fawr was changed to Brynamman in 1864 by the Swansea Vale Railway. A third furnace, called the Big Furnace was added in 1868. Tin works were added across the river in Carmarthenshire in 1872. Central projecting block for charging the furnaces is marked on 1857 map and possibly the two flanking sections. Marked as Amman Brick Works on 1918 OS mapping.

(Source: Cadw Listings database)
S Garfi, RCAHMW, 10/10/2006.