[1][2] King Edward I of England was reputed to have stayed in a house roofed by Cilgwyn slates during his conquest of Wales.

[4] By the end of the 18th century a large number of small pits had grown into a substantial working.

It was then taken over by George Alfred Muskett, a banker from St Albans who served as MP for that city from 1837 to 1841.

Muskett fled the country in 1842, leaving behind debts of £10,000 (equivalent to £1,071,932 in 2016); he died in exile a year later.

[1] In the early 2000s, the quarry was used as a waste dump by the local council, but landfill activity ceased in January 2009.

A mile-long tramway ran from the mills round a horseshoe curve to a waste tip on the north side of Mynydd y Cilgwyn.

[11] The quarry ceased to send slate via the Welsh Highland Railway in 1935 when a new road was constructed down to Talysarn.