Penrhyn Slate Quarry was once the largest and most productive slate quarry in the world. It was the first slate quarry to be capitalised for global markets, reflecting the immense wealth of its owners, the Pennant and Douglas Pennant families. This wealth came from the families’ sugar-growing estates in Jamaica, which were worked with slave labour. The quarry has remained in continuous production since before the capitalisation of the workings by the first Lord Penrhyn from 1782. One reason for the quarry's growth was that Penrhyn slate was favoured and promoted by architect and merchant Samuel Wyatt. In 1898 the quarry employed 2809 men, and 1916 men in 1937-8.

Part of the site remains active, adjacent to the relict historic quarry. The system of benched galleries introduced here at the end of the eighteenth century and the beginning of the nineteenth, now common in quarrying throughout the world, is evident in its relict pit landform, and the immense tips of waste rock dominate both the improved agricultural landscape of the Ogwen valley to north and south as well as the quarrymen's dormitory town of Bethesda.

Within the quarry, the form of its inclined planes is evident, and the two preserved water-balance shaft-heads 'Sebastopol' and 'Princess May' illustrate the means by which slate and waste rock were raised from the lower workings to a large working and tipping area known as 'Red Lion', where a series of mills and range of slate processing shelters known as gwaliau were located. The zip-lines spanning the pit recall the ropeway systems used in the quarry from 1911 to the 1960s. Underground, tunnels and drainage levels preserve a wealth of historic machinery, including a water-pressure engine and associated pumps. One drainage tunnel cut in the 1840s leads from ‘George’ gallery in the pit to an outfall on the Ogwen river, a distance of 1.9 km, and still dewaters the workings. It was cut by experienced miners from Merthyr Tydfil, who brought their Mormon faith to the Ogwen valley, and who departed for Salt Lake City at the end of the contract. The shafts were sunk under the direction of families from the Staffordshire coal-field. Until the late 18th century, slate from Penrhyn quarry was taken by pack-horse and exported from the mouth of the river Ogwen, after this the focus moved to the mouth of the Cegin and Port Penrhyn which was linked to the quarry by a railroad and subsequently, from the 1870s, by the locomotive worked Penrhyn Quarry Railway which operated until 1962.

Penrhyn Quarry holds a significant place in the history of the British Labour Movement as the site of two prolonged strikes by workers demanding better pay and safer conditions. The first strike lasted for eleven months in 1896, and the second began in November 1900 and lasted for three years.

RCAHMW, 4 November 2011.
Louise Barker, RCAHMW, April 2018.

Source:
Louise Barker & Dr David Gwyn, March 2018. Slate Landscapes of North-West Wales World Heritage Bid Statements of Significance. (Unpublished Report: Project 401b for Gwynedd Archaeological Trust).

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Large-scale slate quarrying started at Penrhyn Quarry in 1770 under the ownership of Richard Pennant, who had inherited the Penrhyn estate through his wife, Ann Warburton. Over the next one hundred years, the quarry developed into the largest slate workings in the world, with a workforce of c.3,000 people and its main pit measuring almost a mile in length. With the help of specially laid railways, the slates were transported from the quarry to Port Penrhyn, just outside Bangor, to be shipped to the four corners in the world. Thanks to its high quality and its variety of shades, Welsh slate was considered to be the best roofing material available. It was also used as fencing and building material, flagstones, bespoke furniture, table wear, ornate headstones and decorative masonry.

Conditions in the quarries were life-threatening as the quarry men were suspended from ropes along the rock face and used explosives to remove large slabs of rock. If they did not suffer loss of limb or life, many quarrymen developed silicosis as tiny particles of dust from splitting slates settled in their lungs.

Owing to the adverse working conditions and the notoriously low wages paid to the quarrymen, Penrhyn Quarry saw a number of strikes towards the end of the nineteenth century. Lasting from 1900 to 1903, the Great Strike was the longest labour dispute in British history. It is estimated that nearly a quarter of the population across north Wales was affected. After three years of stalemate, the quarrymen ran out of resources and were forced to return to work at much decreased wages. In the aftermath, orders for north Welsh slate dropped considerably. Since then, slate production has been in decline.

Throughout the nineteenth century, the sheer size of Penrhyn Quarry with its thousands of workers drew a great number of tourists. Rides in the open slate carriages hurtling down the inclines gave great pleasure to Victorian thrill-seekers. Today, the open carts may have disappeared, but tourists continue to zip around the open pit, this time suspended from wires.

Record updated as part of the AHRC-funded project 'Journey to the Past: Wales in historic travel writing from France and Germany'.
R. Singer (Bangor University) and S. Fielding (RCAHMW), 2017.

Penrhyn Slate Quarry is part of The Slate Landscape of Northwest Wales World Heritage Site, Component Part 1. Penrhyn Slate Quarry and Bethesda, and the Ogwen Valley to Port Penrhyn. Inscribed July 2020.
 

Hannah Genders Boyd, RCAHMW, January 2022

Sources:

Louise Barker & Dr David Gwyn, March 2018. Slate Landscapes of North-West Wales World Heritage Bid Statements of Significance. (Unpublished Report: Project 401b for Gwynedd Archaeological Trust)

Tirwedd Llechi Gogledd Orllewin Cymru / The Slate Landscape of Northwest Wales. Nomination as a World heritage Site (Nomination Document, January 2020)

Wales Slate World Heritage Site https://www.llechi.cymru/