Built as Royal Ordnance Factory No. 26 between May 1941 and February 1942, Hirwaun ROF specialised in small arms ammunition manufacture. It covered an area 1.7km east to west by 1.0km. In 1945 the Board of Trade took over the site for use as an industrial estate and it is still used as such today. The site has been extensively rebuilt and there is little evidence of wartime use apart from the general road layout, some minor buildings and derelict sections of concrete roadway; nearby at Hirwaun Ponds railway halt, air-raid shelters provided for factory workers still stand.
B.A.Malaws, RCAHMW, 08 October 2010.