For a period of several centuries, much of the west coast area was once part of the county of Cumberland, Westmorland being the more eastern part of Cumbria. Originally, of course, the two names were synonymous: Cumberland was the land the Cwmry (the brotherhood) whereas the Angles in the east of England referred to this same part of Britain as Westmorland (Westmaringasland–the land of the people who live by the western sea). Few of these Angles reached Cumbria, as is borne out by the relatively low number of English place names. However, they did out of ignorance of Gaelic, add endings of their own. Hence Denu (valley) became to them Dunnerdale (denudael–valley valley).
     How the name Dark valley came to be applied to the area is unknown. A fault line which stretches from the Pink Graphite Igneous Intrusion at far-away Shap, across part of the High Street range and out under the sea close to Millom, goes right over the peak of Coniston Old Man, separating the Coniston Limestone from Brathay flags. For centuries, this could have belched volcanic ash and smoke, causing the area to appear dark. An alternative is that the name could have come from the massive basalt boulder which almost blocks the Dunnerdale Gorge above Seathwaite.
     The River Duddon rises close to the Three Shire Stone (where Cumberland and Westmorland met the County of North Lonsdale–part of Lancashire). It then flows westward from Wrynose Pass through a barren landscape reminiscent of the surface of the moon, as far as Cockley Back where it is joined by its main tributary, Moasdale Beck. Here the fell road splits and one part continues west over Hardnott Pass to Boot and Eskdale. A Roman road once traversed the entire valley, culminating in Hardnott Fort (Mediobogdum). After Cockley Beck, the river turns South-West through a gradually narrowing valley to tumble through the Froth Pot and under the narrow Birks Bridge. It is then joined by Grassguards Gill to fall through the Duddon Gorge below Wallabarrow Crag. Below the pretty village of Seathwaite is the confluence with Tarn Beck, bringing the overflow of Seathwaite Tarn, now a reservoir.
     At Hall Dunnerdale (literally Upper Dunnerdale from the Norse word Hallr meaning high), the roads fork. One goes up and over Kiln bank through the oddly-named Hoses Farm. The other follows the Duddon past the new water works towards Ulpha (wolf-hill). Ulpha has little more than a post-office, church and school. It once had a pub which appeared in the film "The One That Got Away". Below Ulpha, the river races southward to Duddon Bridge and almost erupts into the wide estuary, once dominated by Millom Castle but, more recently, the iron mines on Hodbarrow Point (closed in 1968).
     The lower valley is wide and the river sluggish and has always been difficult to cross because of the shifting soft sands which have claimed many a foolhardy victim. Many proposals have been put forward for a bridge crossing from Askam-in-Furness to Millom, saving many agonising miles of road (cart track) from Barrow, and even a suggestion to make a tidal barrage with which to generate electricity. This, however has been criticised by nature lovers who would seemingly prefer nuclear power from Sellafield.
     Dominating the skyline is the mass of Black Combe at a height of 1970 feet. From here travellers will have the most extensive view from any point in Britain......14 counties in England and Scotland can be seen, together with Snowdon, Isle of Man, and the Mountains of Mourne. Such a view may well explain why William Wordsworth visited here on occasions.