Y Felinheli & Port Dinorwic 

... roughly translates as a "saltwater mill" and the name refers to the old mill on the Afon Heulyn river which was moved closer to the sea in 1633. The area was mostly agricultural until the slate quarrying industry transformed it in the 1800s.

In the latter part of the 18th century the owners of the Vaynol Estate (Y Felinheli and the surrounding area) developed the Dinorwic Quarry and a harbour was needed to export the quarried slate, which was then transported to the harbour by narrow gauge steam railway.