In response to a surge in demand for iron during the Napoleonic Wars the manager of the Blaenavon Ironworks, Thomas Hill II, built what became called Hill's Tramroad from Pwll Du to the Llanfoist wharf around 1815.

[1] This linked Blaenavon via Pwll Du and Garnddyrys to the Brecknock and Abergavenny Canal.

[3] It then ran for 3 miles (4.8 km) north east from Pwll Du round the Blorenge hill to Llanfoist Wharf.

[2] The plans to build the forge in Cwm Llanwenarth on the west branch of the Blorenge included replacing a steeply sloped section of the tramroad from Blaenavon by a shallow gradient tramroad along the Pwll Du Tunnel, an extension of an earlier mine tunnel through the hill to Pwll Du.

[5] The site was abandoned, and is thus important as an archaeologically well-preserved forge from the early 19th century.