OYSTERMOUTH, or The Mumbles, an urban district and seaside resort in the Gower division of Glamorganshire, south Wales, situated on the western bend of Swansea Bay, 4½ m. S.W. of Swansea, with which it is connected by the steam-tramway of the Swansea and Mumbles Railway Company, constructed in 1804. The London and North-Western railway has also a station at Mumbles Road, 2½ m. N. of Oystermouth. Pop. (1901) 4461. The castle, which belongs to the duke of Beaufort as lord of the seignior of Gower, is an imposing ruin, nobly situated on a rocky knoll overlooking the bay. Its great hall and chapel with their traceries Gothic windows are fairly well preserved. The earliest structure (probably only a “peel” tower), built in the opening years of the 12th century, probably by Maurice de Londres, was destroyed by the Welsh in 1215. The early English features of the square keep indicate that it was soon rebuilt, by one of the De Breos lords (see Gower). In 1284 Edward I. stayed here two days as the guest of William de Breos, and from that time on it became the chief residence in Gower of the lords seignior and subsequently of their stewards, and their chancery was located here till its abolition in 1535. The parish church, which has an embattled tower, was restored in 1860, when fragments of Roman tessellated pavement were found in various parts of the churchyard. Roman coins were also found in the village in 1822 and 1837—all indicating that there had been a small settlement here in Roman times. The name of the castle appears in the Welsh chronicles as Ystum Llwynarth, which, by the elision of the penultimate, was probably changed by false analogy into Oystermouth—the bay being noted for its oyster beds. Its church is mentioned in the cartulary of Gloucester (1141) as Ostrenuwe.
The village itself is straggling and uninteresting, but the high ground between it and the pretty bays of Langland and Caswell on the southern side of the headland fronting the open channel is dotted with well-built villas and commands magnificent views. The headland terminates in two rocky islands, which to sailors coming up the channel would appear like the breasts of “mammals,” whence the comparatively modern name, The Mumbles, is supposed to be derived. On the outer of these rocks is a lighthouse erected in 1794 and maintained by the Swansea Harbour Trust. The district is rapidly increasing in popularity as a seaside resort. A pier was erected by the Mumbles Railway Company at a cost of £12,000 in 1898. The fishing industry, once prosperous, has much diminished in importance, but there are still oyster-beds in the bay.