The early history of the quarry is obscure, but it appears to have started around 1825,[3] and was certainly working in 1845, when quarryman John Hughes of Maentwrog fell to his death into the pit, which was then 40 yards (37 m) deep.

[10] In 1896, a major industrial dispute at the nearby Penrhyn quarry resulted in hundreds of quarrymen being locked out and left without work.

[16] On 22 November 1900, the continued friction between the quarrymen an owners at Penrhyn quarry resulted in another strike and lock out.

This was the start of the "Great Strike of Penrhyn", which lasted for three years and was the longest dispute in British industrial history.

In the first month of operation, the quarry turned a small profit and was able to pay wages of 32s 6p (equivalent to £171 in 2018) a week.

In his 1905 address to the union he said: One of the greatest dangers of labour organisations was to fall into the hands of men ... who professed sympathy with the common people merely in order to attain personal ends.

He would say nothing of the agreement which he and others refused to sign, and for which they had been discharged, because, as Mr W. J. Parry admitted, "they had not accepted the terms of the company.

[27] After the First World War, there was a brief boom in the slate industry as a large number of new houses were built in Britain under the Addison Act.

Initially only the grinding operation took place at the quarry, with the dust shipped to factories in Birmingham and Leigh where it was pressed into bricks.

Because this process did not require the firing used to make traditional clay bricks, it was claimed to be a faster and cheaper alternative.

The company purchased a 30 inches (760 mm) Bradley pulverizing machine for grinding the waste and also attempted to build prefabricated houses using slate slabs in steel frame for the walls.

[30] Parry died in 1927, and it appears that this final effort to work Pant Dreiniog for slate failed at or just before this date.

Like most of the local slate quarries, Pantdreiniog had an extensive internal tramway system, of approximately 2 ft (610 mm) gauge.

[33] Parry's enterprise of 1896 saw the quarry re-equipped and the incline was replaced by a lift on the north edge of the pit.