[2] Since its closure in 1969, the quarry has become the site of the National Slate Museum, a regular film location, and an extreme rock climbing destination.

The first commercial attempts at slate mining took place in 1787 when a private partnership obtained a lease from the landowner, Assheton Smith.

Although this was met with moderate success, the outbreak of war with France, taxes, and transportation costs limited the development of the quarry.

The slate vein at Dinorwic is nearly vertical and lies at or near the surface of the mountain, allowing it to be worked in a series of stepped galleries .

[4] The nearby Marchlyn quarry was opened in the 1930s to provide access to the main slate vein higher up the mountain.

Before the bidding started, it was announced that Gwynedd County Council had placed a Preservation Order on the Gilfach Ddu workshops, and many items within it.

The original connection between the quarry and the company's port at Y Felinheli was the Dinorwic Railway, a 2 ft (610 mm) gauge line built in 1824.

The Assheton-Smith family of Vaynol established a tiny wharf on a marshy inlet to convey the output of its Dinorwic quarry in 1793, which marked the beginning of the development of the dock system and related buildings.

It was located directly downstream of a tide-powered grain mill that gave the region its Welsh name, Y Felinheli, and replaced an earlier setup where slate was lightered into the Menai Straits from 500 metres to the southwest.

The  buffer beams on the port locos caused particular difficulties when trying to get them up the inclines to the higher levels of the quarry, but it was achieved.

Docks and quays were constructed in 1809, lock gates were added in 1828, dry docks and engineering facilities were built in the 1830s, a new outer basin was finished in 1854, an outer lock was added in 1897, and a new sea wall was built in 1905 between the harbour and basin to extend the quays.

In 1852, a standard gauge extension of the Chester and Holyhead Railway reached Port Dinorwic, although nearly 90% of the slate continued to be transported by sea, exclusively in rented vessels.

The dry dock was a unique facility in North Wales, making it very valuable to coastal shipping while the vessels were there.

Port Dinorwic was never the fully developed maritime community of the nineteenth century that Porthmadog was, in part because it shared ownership with the Quarry and was devoted to its commerce.

Following closure, the quarry's workshop at Gilfach Ddu was acquired by the then Caernarfonshire County Council, who now lease the building to the National Museum and Galleries of Wales.

In 1987, part of the film Willow was shot in the Dinorwic quarry, on the lower terraces next to the pumped-storage scheme.

Famous British rock climbers such as Johnny Dawes have created well-known extreme test-pieces such as the traditional climbing route The Quarryman (E8 7a) in the Twll Mawr section, and the sport climbing route The Very Big & the Very Small 8b+ (5.14a) in the Rainbow Slab section, of the Dinorwic quarry.