Porthgain harbour lies within a small inlet on the north Pembrokeshire coast, aligned roughly northwest-southeast. Initial use of the site would have been related to fishing and the import of limestone for the lime kiln on the eastern side of the harbour (NPRN 40728). The initial harbour construction at Porthgain dates to about 1850 or 1851 (Davies, 2015: 19) to facilitate the export of slate that was quarried at Abereiddi and Porthgain. A pair of stone breakwaters, western and eastern, were constructed at a narrow point of the inlet, roughly at the low tide mark, along with a small pilot's house at the landward end of the western breakwater. The main berth at this time would have been in the northwestern corner of the harbour, where a stone-built quay wall extended south for c. 30m from the landward end of the western breakwater. The harbour is shown in this overall arrangement on the 1st Edition 25" OS Map published in 1889. Also shown, are a pair of navigation markers on the cliffs to the west (NPRN 525092) and east (NPRN 525091) of the harbour entrance, which it is assumed were built as part of the 1851 construction to aid vessels in locating and entering the harbour. 

From 1889 the quarrying complex was expanded to increase the efficiency of slate extraction, while also quarrying granite, both for slabs, and for crushing. Waste material from the slate industry began to be used in the brickworks, comprising a brickmaking shed (the surviving Ty Mawr), a drying shed and a kiln (both since removed) that was constructed in the centre of the valley (NPRN 40815). Brickmaking stopped in c. 1911. Improvements to the harbour facilities had been planned since the mid 1890s (see Davies, 2015), and work eventually started in 1900 with the installation of a temporary coffer dam to allow the construction of a central stone 'pier', the provision of two berths along the western side of the harbour, and the southward extension of the end of the western breakwater. This work seems to have been finished in c. 1902 or 1903, although photos from after this date (see Davies, 2015) indicate that the extension of the western breakwater was the last stage to be completed to its full height, possibly as late as 1912. The extension can be clearly differentiated from the original structure through the use of concrete and bricks, rather than the stone of the original. At least some work to the eastern breakwater seems to have taken place at this time, evidenced by the concrete facing to its seaward end, and vertical recesses for timbers (since decayed) which match the extension to the western breakwater. Along the western side of the harbour, the northern berth (termed the Hadfield 'H' berth) extended to the original length to c. 40m (130ft), while the southern berth (termed the Baxter 'B' berth) was c. 46m (150ft) in length. The new arrangement of space within the harbour is recorded in the 2nd Edition 25" OS Map published in 1907. The harbour development also included the construction (from c. 1905) of the brick-built storage hoppers along its western side, into which the crushed granite was loaded, ready for shipping. A static crane was located at the end of the central pier, and a mobile crane running on a railway was established along the two berths on the western side and to the end of the western breakwater. The wooden sleepers for the railway survive at the end of the western breakwater.

The final stage of development to the harbour took place in 1930-31. The western side of the harbour was straightened by removing land at the southern corner of the harbour, and lengthening the wall to the west of the central pier. The intention of this work was to create a longer berth, to accomodate larger ships, and resulted in the southern 'B' berth becoming 63m (206ft) long. At the same time, the central pier was shortened to allow better access for the larger vessels into the western part of the harbour. The truncation of the central pier is evidenced by the brickwork at its northern end. Similarily the work to straighten the western side of the harbour can be located through the transition from concrete to brick in the harbour wall to the west of the central pier. Shortly after completion of the final phase of harbour work the company operating the quarries went into receivership and quarrying ceased on 23rd July 1931. Shipments of the remaining stock of crushed stone, followed by stone dust, continued until 1934. The final addition to the harbour was the construction of a concrete slipway down the beach on its eastern side. Porthgain is still a working harbour used by a number of fishing boats, as well as pleasure craft and a rowing club, the latter based in the former brickworks of Ty Mawr.

Some parts of the harbour are designated as a Scheduled Monument (PE382): the western breakwater, berths on the western side, and storage hoppers. The eastern breakwater, central pier and southern harbour wall are excluded from the formally scheduled area. The pilot house is a Grade II Listed Building. The harbour was recorded by the RCAHMW on 27/04/2025 using a photogrammetry survey to create a 3D Digital record of the harbour facilities (links below), as a means to better understand and map their various phases of development.

Sources Include:

Cadw Listed Building 12434: https://cadwpublic-api.azurewebsites.net/reports/listedbuilding/FullReport?lang=&id=12434

Cadw Scheduled Monument PE382: https://cadwpublic-api.azurewebsites.net/reports/sam/FullReport?lang=&id=3644

Davies, P. B. S., 2015. Porthgain & Abereiddi. A Century of Industry. St Davids: Merrivale.

Ordnance Survey 25" Map, 1st Edition, 1889.

Ordnance Survey 25" Map, 2nd Edition, 1907. 

RCAHMW Photogrammetry Survey, DS2025_140, 27/04/2025. View here: https://skfb.ly/pwBSD

J. Whitewright, RCAHMW, May 2025.