[2] The first slate quarry on the site of what was to become Oakeley, was begun in 1818 when Samuel Holland, a Liverpool merchant, leased land near Rhiwbryfdir farm.

In 1821, at the end of the initial three years, Holland took a further 21-year lease on the site, but he sold this in 1825 to the Welsh Slate Company which considerably extended the quarry.

But he managed to avoid the significant industrial action that was interrupting production at other Welsh slate quarries in this period.

The Welsh Slate Company had negotiated a lease extension some years before expiry, so it continued to work Lower Quarry as a separate operation.

Unable to pay the resulting fine, the Welsh Slate Company gave up its lease and the Oakeley was finally amalgamated into a single operation.

At their peak these combined quarries produced 60,000 tons of slate annually and were the third largest in the United Kingdom.

The plant generated the equivalent of 1,930 hp, which was claimed to make it the largest hydro-electric power supply in Great Britain at the time.

Power from the plant was carried to the quarry using an overhead transmission line via Roman Bridge and the Crimea Pass.

[9] The tourist operation included an extensive collection of narrow gauge locomotives, many connected to the Welsh slate industry.

The commercial operation, under the name Ffestiniog Slate Co. reworked parts of the previously underground mine as an opencast quarry.

In 1930 the quarry built an incline down from their Pen y Bont mill to connect to the LNWR exchange yard in Blaenau Ffestiniog.

[10] The track throughout was approximately 2 ft (610 mm) gauge, small enough for workers to move loaded wagons by hand and the same as the Ffestiniog Railway.

Underground the tramways were almost exclusively worked by hand, on the surface extensive use of steam and internal combustion locomotives was made.

The great depth of the mine meant that extensive use of inclines was made to move slate to the mills on the surface for processing.

These had a horizontal upper platform on which 2 ft (610 mm) gauge rails were placed to allow the quarry wagons to ascend and descend.

Nathaniel Mathew, the owner of Middle Quarry pioneered the use of mechanical slate dressing tools at his mill.

The original village of Rhiwbryfdir and the nearby monastery of Mynachlog were purchased by Oakeley and then buried under a massive waste tip.

Space was also sought on the south bank of the Afon Barlwydd and in 1854 the Glan y Don (also known as the Pen y Bont) tip was established.