Blaenavon Ironworks began production in 1789 with 3 furnaces. Two more furnaces were built c1810. The original partnership, led by the Hill family, sold the works in 1836 to the Blaenavon Iron and Coal Co. Initial investment at the site included the construction of a water balance lift for conveyance of pig iron from the site, but further investment did not occur until the 1850s. A new blast engine was built, and a new furnace was blown in during 1861. Investment was also made on a new site kown as Forgeside. By 1900 only one furnace remained in blast, but this was blown out in 1904. Thereafter the site was used by small-scale engineering companies until it became a guardianship monument in 1974.

Furnaces 4 & 5 were built c1810, modified c1880. The stacks were partly taken down in 1911 when the facing stone were used for the building of the church of St James.

A battered masonry furnace casing, the face of which has been mostly robbed out. The tapping arch to the front has also been taken down. The tueyere recesses to the sides have round brick arches. Inside, thehearth, well and the lower part of the boshes have been reconstructed and support the original fabric of the upper part of the boshes and stack.

R Hayman, Hayman & Horton, 6/1/2003