[1][2][3] In 1796 John Curr developed a plateway system, in which flat plates with an upstand for guidance could carry wagons with plain wheels.

The most important waggonway on the estate brought coal from a pit at Cille to Llanelly where small ships were beached for loading, as there was no proper wharfage at the time.

In 1804 the Carmarthenshire Railway was opened; it was an important plateway connecting coal pits near Cross Hands and ironworks to the harbour (which it developed itself) at Llanelly.

Completion of the project was much delayed, taking until 1837, by which time railway technology was clearly overtaking canals as the dominant transport medium.

[2][5][6] A powerful storm breached the main line near Sandy in 1846, and the low traffic volume was not considered to justify the expenditure of reinstatement.

The main line of the canal up the Gwendraeth Fawr Valley reached Cwm Mawr at a considerable altitude, and the upper level had three inclined planes, with gradients of 1 in 13, 1 in 7+1⁄2 and 1 in 10+1⁄4.

A second attempt at the Coal Line was made in the following session of Parliament, and this time it was authorised by the Carmarthen and Cardigan Railway (Kidwelly Extension) Act 1865 (28 & 29 Vict.

[5][7] At this time there were also movements to revive the old Carmarthenshire Railway; this had been built as a plateway in 1804, bringing down minerals from Cross Hands to a harbour at Llanelly.

The authorised capital for the project was £120,000, of which £72,400 represented the purchase price of the canal system; as out-dated technology threatened by viable competitors this was plainly a huge over-valuation.

][note 2] A contractor, Frederick Furness, was appointed on 9 July 1868 and he was prepared to take part of the payment for his services in preference shares.

Under certain bridges the line was laid at a lower level than the towpath, necessitating short downgrades to pass under; nonetheless the headroom at overbridges was very restricted, leading to problems later.

The opening of the main line and these branches encouraged the revitalisation of several pits in the area, by reducing the cost of transport of the mineral to market; however this effect was accompanied by some closures as well.

This loss of the major customer of the line resulted in the BP&GVR not making enough income to pay debenture interest, and it was referred to the Court of Chancery; on 29 July 1881 the company was in receivership.

However a workmen's service was started before the end of 1898, from Burry Port and calling at Trimsaran Road bridge at Morfa to pick up miners who had walked there from Kidwelly.

[2][5][9] The main line was finally completed to Cwm Mawr in June 1886[5][6] (although Miller mentions several other dates put forward by other sources).

[9] The Sandy to Pwll connection was proceeded with, authorised the Burry Port and Gwendreath Valley Railway Act 1891 (54 & 55 Vict.

Lt Col Yorke of the Board of Trade visited the line by invitation to discuss what the proper safeguards might be, and he advised that the Board of Trade "could not recognise the practice of carrying outsiders..." From the careful wording it is evident that the carrying of workmen was condoned, but that it had come to light that the company had been improperly permitting the carriage of members of the general public.

At the same time local people were demanding the operation of a public passenger service on the line; an outlay of £8,500 was calculated to be necessary to enable that, and the work was deferred.

The main line operation was as far as Pontyberem, although a petition had been received from residents at Cwm Mawr for a service; the incremental cost of that would have been £4,000, and there were formidable gradients on that section.

[5][11][12] The possibility of extension of passenger operation to Cwm Mawr was revisited; considerable new earthworks were required to ease the gradient to 1 in 40, and an estimate of £4,844 for the work was arrived at.

Three former London and South Western Railway six-wheel coaches were acquired, to be converted to four-wheelers;[note 5][9] Cwm Mawr was to be supplied with water and electricity from the New Dynant Anthracite Colliery company.

[5][6] In the first years of the twentieth century the production of anthracite in the area served by the railway increased very considerably, and the fortunes and profitability of the company rose correspondingly.

At the end of 1903 the Gwendraeth Valleys Railway Company approached the BP&GVR with the intention of selling their concern; the BP&GVR negotiated but an acceptable price could not be agreed, and the Gwendraeth Valleys Railway later sold its line to the Kidwelly Tinplate Company for £3,000, effective from the end of 1904.

Some traffic was deviated to join the GWR at Kidwelly via Tycoch; previously this route had only been used for coal travelling on towards West Wales.

At the same time silting of the Gwendraeth estuary led to the little quay at Kidwelly being much less used after 1920, and it is believed that the last traffic to use it before closure in October 1929 was roadstone.

[5] In January 1913 the designation of up and down directions was reversed; it had been "up" to Burry Port, but now it was "up" to Cwm Mawr; the reason for the change is not clear, but "up" was now uphill.

The proposed GWR Scheme of Absorption received approval by the BP&GV Board on 20 March 1922 and an Extraordinary Shareholders' Meeting was held on 10 July.

[5][6][14] From 1953 opencast coal extraction gathered pace in the Gwendraeth Valley, and this coupled with economic factors gradually led to closure of most of the deep mines.

The engine was sold off by the Great Western Society and is now in private hands, currently residing at the Pontypool and Blaenavon Railway.

Six examples of cut down Class 03 Shunter that were used on the line still exist today, 03119, 03120, 03141, 03144, 03145, 03152 In May 2016, it was reported that the first trains on the preserved railway could be velorails (pedal powered rail vehicles).