The railway was planned to run between Aberystwyth[note 1] and Pwllheli, and on to Porth Dinllaen, with branches to Dolgelly and Machynlleth.

The former proved impracticable to build, so an altered route was built from Aberdovey to Dovey Junction, near Glandyfi, forming a Y-shaped network.

In 1980, serious defects were found in Barmouth Bridge due to a marine worm boring into timber piles, which took several years to fix.

[note 3][4] Although Machynlleth was an important market town, its promoters were considering an extension to Aberystwyth and the Cardigan Bay coast.

These men shared the idea of continuing to the coast, but Savin's ambitious vision of a huge investment in developing the coastal district was considered by Davies to be over-reaching, and the partnership was dissolved on 30 January 1861.

Porth Dinllaen was a natural harbour on the north side of the Lleyn Peninsula, that had been proposed as a packet station for the Irish mail service.

[10][6][7] The Bala and Dolgelley Railway, friendly to the GWR, had been authorised on 30 June 1862, so that when built it would complete a GWR-supported route to Dolgelly from Ruabon.

[11] Further north, the Carnarvonshire Railway was incorporated on 29 July 1862 with powers to build from Carnarvon to Portmadoc by way of Afon Wen.

The duplication was ignored at first, but the position was finally resolved by an agreement of 13 December 1865 under which the Cambrian Railways (successor to the A&WCR) built the section.

[12][8] The A&WCR concentrated its construction work on the Machynlleth branch, as it was clear that this offered better hopes of early income, compared with the main line crossing the Dovey estuary.

It authorised the construction of an Aberystwyth Harbour branch as well as alteration of the Dovey viaduct and of the Mawddach bridge, to add a vehicular road as well as the railway.

[17][6] (The Aberystwyth Harbour branch was not constructed because the Cambrian Railways as successor to the A&WCR wished such traffic to go to Aberdovey.

[18]) The A&WCR's engineer, Benjamin Piercy, was dismissed early in 1864 as part of a power struggle between Thomas Savin and other factions on the board.

[19][8] In October 1864 preparations were undertaken for a parliamentary bill to authorise the abandonment, and to substitute an extension from Aberdovey to a junction with the Aberystwyth line near Morben.

The bill was given royal assent on 5 July as the Aberystwith and Welsh Coast Railway (General) Act 1865 (28 & 29 Vict.

The act stipulated that the fares and goods rates for consignment between Aberdovey and Borth via Morben were to be the same as if the bridge were built and in operation.

An alternative path around the back of the town was developed, but it was operationally difficult, with steep gradients and sharp curves, as well as three tunnels.

[21] The Manchester and Milford Railway built a line from Pencader to Aberystwyth, opening there in August 1867, with platforms on the south-west side.

On 10 May 1866, the financial house of Overend, Gurney and Company failed, plunging money markets throughout the United Kingdom into turmoil and making railway investments hazardous for the public.

The company's Deputy Chairman, Captain R. D. Pryce, was appointed as receiver; the actions were stayed after two months, at the end of 1867.

c. clxxvii), was passed on 31 July 1868 and authorised a financial reconstruction, as well as preventing for a period the activation of claims against the company; this averted an immediate disaster but did not abate the problem.

In 1913 the company obtained powers for a rail extension to Porth Dinllaen, but World War I intervened and the idea subsequently lapsed.

[30] In 1899, Barmouth viaduct was re-built, described by C. P. Gasquoine as: In 1899, the ironwork portion of [Barmouth] viaduct had become too weak for the constantly increasing loads of developing traffic, [so] it was completely renewed with a modern steel structure of four spans, one of which was a swing span, revolving on the centre pier and giving two clear openings.

in diameter sunk through the sand down to the solid rock, which was reached at a depth of about 90 feet below the high water mark...

[33][23] Aberdovey station, opened at the same time as the "deviation" line to Dovey Junction, was a great distance west of the town, causing complaints lasting for decades.

In the 1960s, the former A&WCR network was under consideration for closure or significant reduction, as goods traffic declined steeply and passenger business transferred to road transport.

The threat of total closure was eventually averted, but the collapse of wagonload traffic, in particular, rendered most local goods facilities unnecessary.

After a partial closure from 13 to 17 December 1964 due to floods east of Dolgellau, the Barmouth to Dolgelly section reopened but finally closed on 18 January 1965.

[32] On 13 October 1980, Barmouth bridge was closed to rail traffic when it was discovered that about three-quarters of the 500 timber trestle piles had been damaged at river bed level by shipworm.

The majority of the line is open, except for the section between Morfa Mawddach and Dolgellau, which closed on 18 January 1965, and the Aberdovey Harbour and Ynyslas wharf branches.