Flagstaff Quarry is an extensive limestone quarry with ancillary buildings that was still in use in 1916, although it was considerably altered circa 1885 to 1916. The remains include: quarry buildings (NPRNs 40626, 40627, 40629, 40633, 40634), limekilns (NPRN 40624), a crushing mill (NPRN 40628), a winding engine, (NPRN 40630), and inclined planes (NPRNs 40631 & 40632). The quarry is shown in use on the Ordnance Survey County Series map (Anglesey XV.61889) dated 1889 and it is recorded on RCAHMW aerial photography.

The quarry is one of the Penmon quarries, where limestone has been worked since the sixteenth century. In the 1890s, fluxing stone for a Glasgow steelworks was supplied from this quarry and a large steam powered crushing plant was built. The double limekiln is a prominent feature.

Source: David Gwyn & Merfyn Williams (1996) `A Guide to the Industrial Archaeology of North West Wales?. Association for Industrial Archaeology

Claire Parry, RCAHMW, 31 October 2011.