The former site of a large complex of copper-working factories established by the Parys Mine Company under the management of Thomas Williams, the 'Copper King'.

Deposits of copper copper were discovered on Parys Mountain, Angelsey, in 1768. In 1774, Thomas Williams of Llanidan, Anglesey, and the Rev Edward Hughes, a local landowner, formed the Parys Mine Company. With the assistance of a London banker, the company began to mine the ore on Anglesey and to send it by ship to Ravenhead near St Helens and to Swansea for smelting, and then in ingot form to Greenfield for the manufacture of various products. In 1783, a new process was patented to produce copper bolts for ships' hulls which could be used to replace the iron bolts used in the ship's construction which were corroded when placed in close proximity to copper sheathing (also produced by the company). The industrial complex at Greenfield soon included a new hammer mill built in 1783, an addtional copper rolling mill built in 1787, and a mill built in 1788 to specialise in the production of copper rollers for printing on cloth (see Meadow Mill NPRN 34068). Forty-six men were employed melting down copper ingots which were moulded into plates and then cut into strips before passing through rollers which pressed the strips into larger, thinner sheets of copper. A trade directory dating to 1790 notes two copper-rolling mills, a brass-making works and foundry, a brass-battery mill, a copper wire mill and a copper forge with hammer mill owned by the Greenfield Copper and Brass Company. For a short period, 1787-1792, the prosperity of the companies linked to the Parys Mine placed virtual control of Britain's copper industry in the hand of Thomas Williams - hence the name 'Copper King'. Thomas Williams died in 1802 . His son Owen continued the company working with his father's chief salesperson Pascoe Grenfell. However, by the early 1800s supplies of cheap ore from Angesley were becoming depleted, and the changes to the shipping channels in the river Dee were making it difficult for ships and barges to reach the Greenfield Wharf. The company's properties and concerns were re-organised in 1814 with Swansea increasing in prominence. Leases on parts of the Greenfield site were allowed to lapse.

The 1870 to 1899 OS maps marked a gasometer adjacent the works, which by 1899 were shown as disused. The gasometer indicated a private gasworks to light the mill.

Sources:
Davies, K and Williams, C J, 1977, The Greenfield Valley, published by Holywell Town Council