Porth Amlwch is a natural harbour formed in a creek between high rocks and is about 500ft long and 100 ft wide at its entrance. Whilst in use since early times, the general form and layout of the harbour dates from the late eighteenth century when the port became the main port and smelting site for the copper mines in North Wales, most significantly that at Parys Mountain. It also developed as a ship-wrighting port and has a surviving shipyard (NPRN 41251), dry-dock (NPRN 41246), and sail loft (NPRN 41249). The port is joined to the town by Lon Gopar (Copper Road).

In 1740, Lewis Morris who had been commissioned by the Lord of Admiralty to survey the coast of Wales, described the cove as 'little more than two steep rocks where a vessel have no room to wind even at high-water. But where a large vessel might be saved here, in case of necessity, provided the mouth of the harbour can ve discovered, which is now difficult for a stranger'. Two white houses provided the navigation marks for mariners, one each side of the harbour's mouth. Exports included corn, butter, and cheese from local farms. Liverpool pilot boats were also known to wait here on the lookout for vessels needing their services to enter the Dee or Mersey. The discovery of vast amounts of copper at Parys Mountain in 1768 began to see improvements to landward eastern side of the inlet. Wharf building back directly onto the water's edge for loading. A small pier was built by the Paryus Mining Company in 1782, but was later removed to aid further port development. Use of the harbour continued to increase and an Act of Parliament was passed in 1793 to provide for deepening, widening and better regulation. A board of Harbour Trustees was established and set about developing teh eastern side of the harbour. Some 20,000 tons of rock face was quarried away to form a new wide quay on which were built several storage bins. The rock was used to create a new quay. The western side of the harbour was given over to shipbuilding. The first shipward was founded here by Nicholas Treweek. He established a new yard outside the harbour, to allow for the buidling and repair of ever large vessels. The old yard was sold to William Cox Paynter who specialised more in ship repair than ship building. Nicholas Treweek entered into partnership with Captain William Thomas in 1859 to initially share ownership the schooner GRACE EVANS, but by 1872 William Thomas had taken over. The firm of William Thomas & Son continued until the death of William Thomas Junior in 1930. Open to the north, the harbour was subject to dangerous storm surges and ship masters were required to provide men to help haul large 13 balks of timber across the harbour mouth, in place of gates and let down into grooves. A mast was errected at Llancarw and a cask woudl be hauled to the top to notify mariners that the the balks were in place. This provision was not always sufficient to prevent disaster. For example, on the night of 20-21 March 1889, four vessels were severely damaged and another which had been in the dry dock was floated and smashed to pieces against the pierhead (NPRN 240183 EMPORER). Control of the harbour passed to the local authority in August 1913 when the Harbour Trust was wound up.

RCAHMW, July 2012.