"LLANDDEINIOLEN, a parish in the hundred of Is-Gorfai, county Carnarvon, 4 miles N.E. of Carnarvon, its post town, and 6 from Bangor. It is situated at the head of the vale of the Cegid to the N.W. of Snowdon, and E. of the Menai Straits. The parish, which is very populous, includes the villages of Clwt-y-Bont, Ebeneza, and Penisarwain. The old Roman road passes through it. The people are mostly employed in the Dinorwig slate quarries. There are several mineral springs. The tithes were commuted in 1839. The living is a rectory* in the diocese of Bangor, value £305, in the patronage of the lord chancellor. The church is a small ancient structure. The parochial charities produce about £6 per annum. In the neighbourhood are some objects of antiquarian interest, including a rocking stone, a Druidical circle, and cyttian, the ruins of the palace of Llewelyn ap Grufydd, the last of the princes of North Wales, at Llys Dinorwig, and the pass of Nant-y-Garth, through which it is said Archbishop Baldwin and Giraldus passed in 1118." [From The National Gazetteer of Great Britain and Ireland (1868)
Deiniolen grew up around Ebenezer chapel of c. 1824 (hence the old name ‘Ebenezer’ for the village) from around 1830. Today Deiniolen is a village in Gwynedd, Wales, at the foot of Elidir Fawr. On a clear day, Deiniolen has views covering the Wicklow Mountains in Ireland, Caernarfon (7 miles away) and Holyhead Mountain. The slate industry was an important employer in Deiniolen, but since the closure of the quarry in 1967, the economy of the village has been in decline.
Saint Deiniolen was the son of Deiniol of Bangor. His name contains the diminutive ending -en 'little' deiniol. He was also known as Deiniolfab (son of Deiniol).
Llanddeiniolen is the name of the parish, a large parish which contains more than one village. Deiniolen is a modern name, adopted early 20th century, for the village which was called originally Ebeneser (named after the chapel) which was considered non-Welsh. The name was adopted from the parish name.
Deiniolen also exemplifies the earliest types of purely industrial housing in Gwynedd, apparently uninfluenced by vernacular agricultural dwellings, beginning with the tiny and shoddily-constructed houses along the slate road, dating from the 1820s, the more substantial Rhes Fawr, and the two-up-and-two-down houses built in the 1860s.
Clwt y Bont is more typical of early industrial settlements in Gwynedd in that it is less apparently planned, and the characteristic short terraces built into the slope are evident here. Its plan recalls and preserves the course of the Dinorwic Railway of 1825. The sites of some of the mills are evident, and some grew into workshops of significant size, which remain in use.
The social infrastructure of the two villages is impressive, though much of it evidently had to be constructed at a little distance from the main housing stock. As well as the mid nineteenth-century chapels, the substantial Kennedy church and the schools, the Carnegie library is an attractive feature.