Although there has been a dock or landing stage on the River Conwy at Deganwy in North Wales since the twelfth century, the modern development began with competition between railway companies over the transport of high-quality roofing slate quarried at Blaenau Ffestiniog to a port and thence by sea to the towns and cities of Britain and beyond. Unfortunately the Conwy Valley line between Blaenau Ffestiniog and the dock at Deganwy never fulfilled the high expectations of the railway owners who built it.
In 1882, three years after the opening of the Blaenau extension, the London and North Western Railway Company finalised its plans for building a 20 acre dock at Deganwy with the intention of centralising all its seagoing slate traffic, work commencing in 1883. Towards the end of the nineteenth century the demand for Welsh slate began to decline due to higher labour costs, importation of cheaper, poorer quality slate from abroad (notably France) and competition from clay roofing-tile manufacturers in England. By 1914 the Welsh slate industry had lost half its capacity and the railway dock at Deganwy was working at only a fraction of its potential. The dock had been built at least ten years too late and was a monument to the greed and over-ambition of the LNWR.
After 1918, the decline in dock traffic continued and ceased altogether in the 1930s. By this time a new industry began at the dock: boat-building. After the Second World War and railway nationalisation, Deganwy Dock was used by British Rail to store vintage railway coaches that were at the end of their useful life but kept for the formation of special land cruise trains. Boat-building continued but by 1970 the railway lines at the dock had been removed and the place had fallen into decay. Since 2000 the dock has been redeveloped into a marina alongside the construction of houses and apartments.
Source:
E.Smith, The Deganwy Dock Story (2013), from http://www.deganwyhistory.co.uk/

RCAHMW, 18 June 2015