The Sirhowy Ironworks was established in 1778. From 1794 to 1818, it was operated and managed Borrow, Rev'd Monkhouse and Fothergill. By 1818 the works belonged to James Harford of Harford, Partridge and Co. of Ebbw Vale. After this they were operated in conjunction with Ebbw Vale Ironworksto the east. Sirhowy supplied pig iron to Ebbw Vale for working into wrought iron.
At the end of the 19th century onwards the iron supplied was converted to steel.
On site today the furnace at the south end is one of the oldest there however by 1899, it was in use as a limekiln.
In 1844 Abraham Darby & Co bought both works at which point there were five furnaces at Sirhowy.
In 1877 the site was reconstructed for Hot Blast. Two furnaces which stood in front of the two smaller arches were demolished and replaced with a large tower type furnace which was taller than the existing furnace wall. An air hoist was used to charge the raw materials into the furnace top.
Waste gases were piped from the backs of the furnaces using cast-iron pipes and were burnt in the ovens. Within the arches to be found on site are blast passages through which a cast-iron main brought air from the steam powered blowing engines to the hot blast ovens. The heated air from these then ran to the furnaces.
By 1877 the amount of iron cast produced exceeded the capacity of the cast house leading to their partial demolishion.
After ironmaking ceased at Sirhowy circa 1883 it produced coke for Ebbw Vale until final closure of the site in 1905.