In 1825 local industrialists and landowners obtained an Act of Parliament for building a tram road down the Llynfi valley to Porthcawl bay, and improving the bay by the erection of some form of dock. The line began at Dyffryn Llynfi, a few miles above Maesteg, and ran along the valley to Tondu where it turned westward towards Kenfig Hill and through Pyle and Newton Nottage to reach the sea at Porthcawl. Other sites at the mouth of the Ogmore River and at Newton had been considered for the dock but were rejected, either because of difficulties of terrain or because the landowners were uncooperative. The harbour built at Porthcawl was a small rectangular basin which was tidal and so could only be used at certain times of day, and in 1840 it was extended and deepened. By 1864 the growth in the iron and coal industries was such that the two railway companies which then operated in the Llynfi and Ogmore valleys joined forces to obtain a further Act proposing much greater expansion.
The entrance to the existing basin was to be re-positioned, and a completely new dock of some 7 acres area would be built, connected to it, on the north, and fitted with gates so that it would not be dependent on the tides; the breakwaters would also be extended. The new dock opened in July 1867 at a cost of £250,000, and in seven years the amount of coal exported increased almost ten times.
Depression in the iron industry led the dock to concentrate more and more on coal. Trade reached its peak in 1892 when over 800 ships docked, but it declined very rapidly after that, largely because of the opening of more expansive and modern docks at Port Talbot. Trading from Porthcawl finally came to an end in 1906, and the town turned its attention from commerce to recreation.
Glamorgan Archives holds 32 plans prepared by the London engineer R.P. Brereton between 1864 and 1866 for the extension of Porthcawl Dock (ref.: UDPC/HARBOUR). The collection of plans, though comparatively large, may not be complete; some of them are numbered, but not all the numbers are present. As well as an overall plan, they show details of the dock gates, the breakwaters and coal lines. On the ground the dock of 1867 has been filled in, but the plans survive as a reminder of one aspect of Victorian industrial growth, and the changing fortune of different ports.