This post is prompted by reading a short set of notes about the Penydarren Tramroad carried in the Railway Magazine in March 1951. 
Merthyr Tramroad, or the Penydarren Tramroad, ran from quarries near Morlais Castle via a junction on the Dowlais to Jackson’s Wharf tramroad at SO 0512 0669 (at the present junction of Tramroadside North and Penydarren Road and now marked by the Trevithick Memorial (NPRN No. 91516)) in Merthyr Tydfil, to the Glamorganshire Canal basin at Abercynon (ST 0846 9493) where a commemorative plaque has been erected (NPRN No. 400379).
The tramroad was built because the Dowlais Company’s tramroad ran past the Penydarren Ironworks on a high level course, making it impossible to build a junction for the Penydarren Ironworks to use. In response, Samuel Homfray of Penydarren Works commissioned the tramroad to follow the eastern bank of the River Taff down to Navigation (modern day Abercynon). The tramroad was completed in 1802, and was in use until 1875, except for a period of uncertain length starting in 1815 (and maybe continuing to 1825) because of the collapse of a bridge at Edwardsville just north of Quakers Yard. 
Essentially, the Morlais Quarry section was built to supply Merthyr’s Ironworks with limestone, and the Merthyr to Abercynon section to avoid the congested Glamorganshire Canal (NPRN No. 34425). 
To accommodate the horses, the tramroad didn’t use sleepers as we’re now used to from our modern railways. The rails sat on two lines of stones, allowing the horses to walk between the rails without difficulty. It also made things easier for the man who led the horse throughout the journey! There are several good examples of the tramroad stones still in existence along the route. Today, the rails are gone, but the tramroad formation still exists, and can be followed from Abercynon up to Merthyr Tydfil. The entire length up to Pontygwaith is part of the Taff Trail route of the National Cycle Way. 
“The tramroad and the system of which it formed the major part had two other important and interesting features which are less well known: the permanent way of the first railway in the area and the series of early industrial locomotives (most of them Welsh-built by Neath Abbey Ironworks) that traversed the line in the 1830s and 1840s. … The history of these lines is complicated, confusing and at times conjectural.”  Many of the notes below come directly from a blog written by M.J.T. Lewis entitled, “Steam on the Penydarren” which is held in the archives of the Industrial Railway Society.  These notes are supplemented from other sources, as referenced.
“The major industrial development of South Wales began in the 1780s and especially the 1790s. In Taff Vale and some of the other valleys the main commodity involved was not coal – the real growth in that trade only came later – but iron. Resources were plentiful and demand good; only transport was lacking. It was the canals that began to open up the country, with a series of roughly parallel routes up the valleys, dating mostly from the 1790s. The terrain often prevented these canals from actually reaching the industry, so that feeder railways proliferated.” 
The Glamorganshire Canal was opened from Merthyr down to Pontypridd in 1792 and to Cardiff in 1794. It served Cyfarthfa (see below) directly, and the Dowlais Works has to lay a two-mile railway to carry its iron down to a basin at Merthyr Tydfil. This line was complete by June 1791, and cost about £3,000 of which the Canal Company, wishing to attract traffic, paid £1,000. The gradient was very steep – an average of about 1 in 23, with a maximum of 1 in 16½ – and horses worked the waggons in both directions. 
“There were three ironworks to the east of Merthyr Tydfil. Dowlais (begun in 1759) grew rapidly in the early 19th century, until in 1845 it was the largest ironworks in the world, employing a workforce of 10,000. The others were smaller: Penydarren works (1784), adjoining Dowlais on the south and west, and Plymouth (1763), to the south of Penydarren, which established several offshoots nearby – in 1803 a forge and later a rolling mill at Pentrebach, and in 1819 a group of furnaces at Dyffryn. Neither Plymouth nor Penydarren developed nearly as fast as Dowlais. All three companies, sooner or later, mined or quarried their own ore, coal and limestone, and all had their own railway systems leading between the various branches of their undertakings. All three produced primarily pig iron, but converted an ever increasing proportion of it to wrought iron, and as Railway Age got under way they came to concentrate on rolling rails.” 
The Cyfarthfa works were begun in 1765 by Anthony Bacon (by then a merchant in London), who in that year with William Brownrigg, a fellow native of Whitehaven, Cumberland, leased the right to mine in a tract of 4,000 acres land on the west side of the river Taff at Merthyr Tydfil.  The heyday of the works was in the tenure of Richard Crawshay (1739-1810) and the works went into gradual decline thereafter. The Dowlais Works became the leading Ironworks in the Valley.  As we have already noted, the Cyfartha Works were directly served by the Glamorganshire Canal. This was not the case for the Dowlais, Penydarren and Plymouth Works. Because the owners of the Cyfarthfa Ironworks dominated the management of the Glamorganshire Canal, the other Merthyr Tydfil ironworks built a tramroad bypassing the upper sections of the canal. 
We have already noted that the Dowlais Works became the largest ironworks in the world in the early to mid-1800s. The Works, founded in 1759, owed much of their success in the 1820s to the production of rails for the railway and tramway industry in the UK.  In the 1850s, the Works was the first UK organisation to licence the Bessemer Process for the production of steel. The first Bessemer steel was actually rolled at the works in 1865. Unlike the Cyfarthfa Ironworks nearby, the Dowlais Ironworks converted to steel production early allowing it to survive into the 1930’s.  The Dowlais Steelworks. 
The Penydarren Ironworks were founded in 1784 and operated independently, but at times sporadically, until the late 1800s.  The Dowlais Works bought mineral ground of the Penydarren Works in 1859. The Penydarren Ironworks, © Bronwyn Thomas 
Initially a tramway was built for the Dowlais Works alone to reach the canal near Mertyr Tyfil. We could call this the first Dowlais Tramway. There is record of a dispute between the proprietors of the Dowlais Works and the Penydarren Works. The result appears to have been that Penydarren built their own railway to the canal, closely paralleling the Dowlais line and in places right alongside it. The date was somewhere in the 1790s, but the original type of rail and gauge are quite unknown. This railway, though not the Dowlais one, had a short tunnel under Bethesda Street in Merthyr. 
Up to this time, all railways had wooden trackwork. In the north of the UK, a gauge in the 4ft to 5ft range and waggons holding up to 3 tons were the norm, with the wooden rails occasionally protected against wear a tear by thin wrought iron plates. The West Midlands and Wales, however, followed the example set by the Shropshire collieries and ironworks, which favoured narrower gauges (up to 3ft 6in or so), smaller waggons and sometimes flat cast iron plates laid on top of the wooden rails. 
“This form of protection was introduced at Coalbrookdale in 1767, but rail made solely of cast iron, only appeared in 1791. This happened in South Wales, an area that always looked towards Shropshire in mining, ironmaking and transport, and the line involved was the Dowlais-Merthyr railway. William Taitt of Dowlais wrote on 17th March 1791: ‘We are now making Rails for our own Waggon way which weigh 44 li or 45 li [Ib] per yard. The Rails are 6 feet long, 3 pin holes in them, mitred at the ends, 3 Inches broad Bottom, 2½ In. top & near 2 In. thick thus:'” 
As far as is known, these were the first all-iron rails ever made for flanged wheel railway. It was copied in the next few years on a number of feeder railways to the Monmouthshire and Brecon & Abergavenny Canals. The gauge of these lines was 3ft 4in, they were engineeered by the Dadford family and as the Dadford’s also engineered the Dowlais tramway, it is likely that this would have been the track-gauge of the line. 
Because of difficulties in sourcing materials, the Dowlais Works built a second tramway from the Morlais quarry to the works. (Penydarren owned the western part of Morlais quarries and Dowlais the eastern part, and both no doubt began by carrying the limestone to their respective works by cart.) This second tramway was probably built in 1792, it’s course is uncertain but probably approximated to the future Brecon & Merthyr Tramway from Pantyscallog to Dowlais Central. Whether Penydarren had its own tramway from Morlais in the 1790s is not known. 
The story clearly does not end there, Dowlais Works constructed another plateway/tramway in the 1790s linking its colliery, probably to the south-east of the Works to the Works. 
In the late 1790s, the accepted design of plate-ways/tramways in South Wales changed. Old edge-railways with flanged wheels were replaced by flanged (usually L-shaped) rails and wagons were fitted with plain wheels. “Practically always, the rail ends were set on separate stone block sleepers instead of on transverse wooden ones. In early days the rails were simply spiked down, through notches at their ends, into wooden plugs in the blocks; later, chairs were introduced and even cast iron cross-ties which, though not spiked down, were held on the blocks by the weight of ballast, the rails being fixed in dovetailed sockets.”  George Overton was a protagonist for the new plate-ways and was ultimately responsible for the Penydarren Tramroad. 
The later Penydarren Tramroad owed its origin to a quarrel between Richard Crawshay of Cyfarthfa and the ironmasters of Dowlais, Penydarren and Plymouth. Crawshay had a controlling interest in the Glamorganshire Canal Company and claimed preferential treatment in the matter of carriage, to the detriment of the other Merthyr works. The Glamorgan-Gwent Archaeological Trust comments: “The Penydarren Tramroad from Penydarren to Abercynon was constructed in 1802 because of disagreements over tariffs charged on the Glamorganshire Canal between Richard Crawshay of Cyfarthfa, who held the largest share in the Canal Company, and the owners of the other iron works of the area, Penydarren, Dowlais and Plymouth.” 
The three iron-masters petitioned Parliament in 1799 for a tramroad from Cardiff with branches to Merthyr, Abernant and the head of the Rhymney valley. The Bill “was defeated by canal opposition, but already, on 18th January 1799, Samuel Homfray of Penydarren, William Taitt of Dowlais and Richard Hill of Plymouth had agreed to build the section from Merthyr to Abercynon: by‑passing, that is, the upper and most inconvenient stretch of the canal. The tramroad was built without an Act; compulsory powers, though not invoked, were already provided by the Glamorganshire Canal Act, which authorised proprietors of works within four miles of the canal to build railways to it. Dowlais and Penydarren each owned five shares in the tramroad, Plymouth four. The line was built under the general supervision of Richard Hill; George Overton was the engineer. ”  Work began in 1800, and the tramroad was completed in 1802. It was 9½ miles long from a junction with the Dowlais-canal line in Merthyr to the canal basin at Abercynon. The gauge was 4ft 2in inside the plate flanges, or 4ft 4in over them. Dowlais Ironworks in 1840. Watercolour by G. Childs [British Steel Corporation] 
“At about the same time there were considerable changes to the private Penydarren and Dowlais systems. The Dowlais-canal line, above the new junction with the Penydarren Tramroad at Merthyr (where the Trevithick Memorial now stands) was converted to 4ft 4in plateway, so that through running from Dowlais to Abercynon was possible; the lower part, from the junction to the canal at Merthyr, was apparently closed. The Penydarren Company’s line to the canal remained, consisting now of plate rails at 3ft outside gauge – the standard Penydarren Company gauge.” 
“About 1800 a new tramroad was built from the western Morlais quarries via Goetre Pond to Penydarren works, as part of the general agreement to make the Penydarren Tramroad. … In 1803, the three ironmasters agreed to add 4ft 4in track to this Morlais-Penydarren tramroad, ‘the present Road to remain on the inside of the Wide Road’, and the stone blocks once visible indicated three-rail track. The purpose of this dualling of the gauge was to permit through running via the Penydarren Tramroad to Plymouth works, and thus to free Hill from his bondage to Crawshay in the matter of limestone. The Morlais line became a part of the “General Road”, paid for initially according to the shares each ironworks held, and maintained thereafter according to the tonnage carried by each.” 
Also in about 1800, Overton converted each of the Morlais-Dowlais tramway and the Dowlais Colliery to the furnaces tramway into a plateway. The result of these changes was significant. Prior to the alterations one horse pulled one wagon, “now ‘each horse regularly hauled from the farthermost part of the colliery twelve [wagons], carrying fifteen hundred-weight each, and took the empty ones back’. As was usual in such cases, the exact route of this line was frequently altered as new pits were opened and old ones closed. Penydarren also had its own coal lines, which included inclines, on the 3ft gauge and going in the same general direction as the Dowlais ones.” 
1804 saw the famous trials of a steam locomotive on this tramway. The Route of the line, and that taken by Trevithick’s locomotive, is shown on the adjacent sketch drawing from The Railway Magazine from March 1951.  … Richard Trevithick “was, in October, 1803, busily engaged in constructing at Penydarran, in South Wales, a tramway locomotive, to run on rails not exceeding an elevation of 1 in 50, and of considerable length.”  On 21st February 1804, the locomotive was active on the Penydarren Tramway with a “full supply of steam and power.”  Indeed, “before a week had passed, from the first getting-up of steam, this pioneer of railway-engines had run several times, drawing a load of 10 tons, and was more controllable than horses. Only two miles of road were to be run over during the first trials, but within the week the engine ran a distance of 9.75 miles.”  Trevithick’s locomotive was the first steam locomotive to pull a load on a railway. 
The engine in working order weighed about 5 tons its cylinder was 8.25 inches in diameter, with a stroke of 4.5 feet. It took empty wagons up an incline of 2 inches in a yard, at forty strokes a minute, progressing 9 feet at each stroke in other words, it took its load up an incline of 1 in 18 at the rate of four miles an hour. Deatials of the locomotive were provided in an article in the March 1951 edition of The Railway Magazine. Although the tramway was the route used for this first-ever steam-powered railway journey, those early iron rails couldn’t take the weight of the engine. The tramroad soon reverted back to using horses to draw the wagons down to Navigation (Abercynon). Dowlais furnace tops and tram waggon, 1840. Watercolour by G. Childs. [British Steel Corporation] 
The Penydarren or Merthyr Tramroad clung to the hillside on the east side of the Taff for almost all the way, with the gentle average gradient of 1 in 145. Apart from the occasional road bridge and culvert, it had only three engineering features of note. At Plymouth works, the line passed right underneath the charging area of the furnaces in a tunnel 8ft high and 8ft wide: ample clearance for horse-drawn trams but a distinct impediment to locomotive working. Two bridges carried the line across a large loop of the Taff near Quakers Yard, both of which began life as timber structures. The Wikipedia article about the tramway says: “In 1815 a wooden bridge over the Taff near Quakers Yard collapsed beneath a train carrying iron from Penydarren. The whole train including the horses, the haulier and four other people riding on it fell into the river killing one horse, badly cutting another and injuring two of the people.”  Both timber bridges were replaced by large stone arch bridges.
“The Penydarren was a single-track tramroad with frequent passing loops. The original track consisted of 3ft‑long cast iron plate rails with upward-bellied flanges and a strengthening rib below; they weighed about 60 lb each and were spiked directly to rough stone blocks about 1ft 6in square. Later, chairs were introduced to provide a better bearing surface and a new pattern of rail that instead of a spike-notch had a downward projection to prevent longitudinal movement. These rails were keyed in the chairs. A third type of rail was a dual-purpose one, with both notch and projection. All this ironware was doubtless cast at the three ironworks interested in the line. Many blocks are still in position from Mount Pleasant southwards, and some rails may be seen in the Cyfarthfa Museum at Merthyr. … When locomotives were introduced the continual breakage of plates under their weight created a serious problem, but cast iron rails were retained to the end.” 
“The trams (or wagons) were about 7ft 6in long by 4ft 9in wide at the top, each side consisting of a vertical plank 1ft high topped by a flared plank 9in high. The bodies were originally of timber strapped with iron, though later 1/8in plate iron was adopted. The cast iron wheels were usually 2ft 6in to 2ft 9in in diameter, with a tread 1¾ in wide. A tram’s capacity was two tons or a little more, and its weight was 15cwt By 1830 there were 250 of them..” 
Early on, one horse would pull five trams (a total of about 10 tons of iron) down and the empties back up, making one return trip a day.As demand increased, so did the length of tram trains. As many as three horses could be teamed up and would haul about 25 trams (about 50 tons of iron). Although the line was privately built, other parties were allowed to carry goods on it on payment of a toll; but it is not known if this ever happened. Passenger traffic, though quite unofficial, was winked at: anyone who was ready to tip the driver and to perch on a tramful of iron was allowed a ride.
“The traffic consisted largely of iron for export from Cardiff, and grew markedly for much of the tramroad’s life. In 1820, Dowlais sent down 11,115 tons of iron, Penydarren 8,690 tons and Plymouth 7,941 tons; in 1830, the respective tonnages were 27,647, 11,744 and 12,177; and in 1840, 45,218, 16,130 and 12,922. From the late 1820s, however, more and more iron ore was imported, a traffic which came to outstrip the tramroad’s capacity on the uphill haul, so that the bulk of it was carried by canal up to Merthyr and transferred to the Penydarren Company’s line there.” 
In 1835, Dowlais alone imported 15,668 tons of ore and cinders. To deal with the increase in both traffics, locomotives were introduced. Trevithick’s engine had hauled several trains to Abercynon in 1804, but it was simply an experiment which was only a partial success. Regular locomotive working began in 1832, when an engine owned by the Penydarren Company was closely followed by a series belonging to Dowlais, some of which worked the steep section up to Dowlais with the aid of a rack rail laid between the running rails. However, the tramway was becoming increasingly outdated and the Iron Works needed a better method of transport.Penydarren Ironworks in 1813. [J.G. Wood, “The Principal Rivers of Wales Illustrated”]Bethesda Street, Merthyr, looking east. The car is standing on the route of the Penydarren Company’s line to the canal, with Bethesda Street tunnel beyond; the Dowlais Company’s line to the canal ran along the street to the left. [P.G. Rattenbury]
“As early as 1823 they promoted a Bill to extend the tramroad to Cardiff – again the primary cause was a quarrel with the Glamorganshire Canal Company – and again the Bill was lost. In the end, with Hill of Plymouth and Guest of Dowlais among the chief promoters, the Taff Vale Railway obtained its Act in 1836, and was opened from Cardiff to Abercynon in 1840 and to Merthyr in 1841.” 
The Taff Vale had powers to make branches to the ironworks, but nothing was done until in 1849. Dowlais obtained its own Act for a standard-gauge line from the works, via a long incline, to the Taff Vale at Merthyr. This was opened in 1851, at first as a public passenger railway, but later carrying the owner’s goods traffic only. 
From 1841, Dowlais sent out considerable quantities of traffic from the Taff Vale Railway (TVR) terminus at Merthyr, but it is not clear how produce was transported to the terminus from the Works. The TVR station was actually very close to the Penydarren Tramroad. Dowlais stopped using the Penydarren Tramroad by 1851 if not before, and it seems likely that the tramway between Dowlais and Penydarren Works was abandoned at the same time. Victoria Bridge, the lower Penydarren Tramroad bridge across the Taff at Quakers Yard. The piers beyond carried a feeder to the Glamorganshire Canal. [collection T.J. Lodge]  Penydarren Tramroad stone block sleeper, showing impressions of the rail ends and the single spike hole. [T.J. Lodge] Road bridge over the Penydarren Tramroad half a mile south of Mount Pleasant. [T.J. Lodge] Crossing of a set of points with scallop-edged channel rails for level crossings. [P.G. Rattenbury] Trackbed of the Moralis-Penydarren tramroad, showing rows of stone blocks which carried the dual gauge track. [collection T.J. Lodge] 
Thereafter the tramroad fell out of use piecemeal. When Penydarren works closed in 1859 the section down to Plymouth was probably closed too. Plymouth went on sending some iron down to Abercynon for a while, but ceased to produce iron in 1880, though it continued its coal mining. Already, in 1871, Plymouth had built a standard gauge mineral line that used parts of the tramroad route as far as Mount Pleasant; south of here the tramroad seems to have been lifted about 1890. As we have already noted, the Merthyr/Penydarren Tramroad was largely superseded when the Taff Vale Railway opened in 1841 and sections gradually went out of use over the two decades from about 1851. In 1823, a Bill had been unsuccessfully promoted to extend the tramway to Cardiff. It was some of the same promoters who obtained the Act for the TVR in 1836. Although the TVR opened to Merthyr in 1841 it wasn’t until 1851 that the standard gauge Dowlais Railway was completed allowing through running to its works. Penydarren Ironworks closed in 1859. Plymouth Works didn’t cease iron production until 1880 but had built a standard gauge line over part of the tramroad in 1871. South of Mount Pleasant the disused tramroad was lifted in about 1890. 
“In 1829 Stephenson supplied a six-wheeled locomotive with inclined cylinders mounted at the rear for use on the narrower gauge internal lines at Penydarren, it cost £375. In 1832 it was returned to Stephensons for conversion to a four-wheeled locomotive for use on the Merthyr Tramroad and at the same time the single flue was replaced by 82 copper fire tubes. It was at this time given the name “Eclipse” and commenced work on the Merthyr Tramroad on 22 June 1832. The chimney must have been hinged to allow it to go through the Plymouth tunnel.” 
“The Dowlais Company’s line linking their works to the Merthyr Tramroad had a maximum gradient of 1 in 16.5 and considered too steep for locomotives to work by adhesion alone. In 1832 the Neath Abbey Ironworks supplied a six-wheeled rack and adhesion locomotive weighing 8 tons named “Perseverance” with inclined cylinders and twin chimneys (allowing them to be lowered alongside the boiler to pass through the tunnel at Plymouth).” 
Another similar locomotive named “Mountaineer” was built in 1833 by the Neath Abbey Co. for the Dowlais Company. The drawings included a cross section of the Plymouth tunnel and it had a hinged chimney, so it is very likley that it was intended for use on the Merthyr Tramroad (unlike a second smaller locomotive built in 1832 which had a fixed chimney). 
The Wikipedia article on the Tramway continues to use information provided by Stuart Own-Jones  to describe locomotives used on the line:
The 0-6-0 “Dowlais” built at Neath Abbey in 1836 had inclined cylinders mounted at the front (unlike the previous locomotives which had rear mounted cylinders) and rack drive for use on the incline to Dowlais. “Charles Jordan” delivered from Neath Abbey in 1838 was an adhesion only locomotive very similar to “Mountaineer”. The last record of spare parts being supplied to Dowlais for these locomotives was in 1840-1841. An 1848 inventory of Dowlais plant lists only “Mountaineer” of the above locomotives. No plateway locomotives were listed in 1856. 
Locomotives had a maximum 3 ton axle load and as a result plate-layers were carried on the trains to replace broken plates. On 1 April 1839 more than 4,000 plates were required to make the tramway good. By 22nd June that year 1,600 more plates were broken, of which the Dowlais engines were blamed for smashing 1,450. By July the tramroad was reported to be almost impassable, for two days being blocked by a derailed Dowlais locomotive and Anthony Hill of Plymouth unsuccessfully applied to the Trustees for the locomotives to be banned. 
Stuart Herbert  provides a lot of additional sources to allow a deeper exploration of the history and geography of the line. These include:
- The Glamorganshire and Aberdare Canal – Volume 1, by Rowson and Wright.
- Richard Trevithick: Cornwall’s Pioneer of Steam, by the South Western Electricity Historical Society
- ENGINEERS: Richard Trevithick the Cornish genius, by Cotton Times
- Trevithick 2004, a joint public/private/voluntary sector partnership to celebrate the 200th Anniversary of the Penydarren Locomotive – the first steam locomotive in the world to haul a load on rails.
- Cynon Culture, a website dedicated to the history and culture of the Cynon Valley.
Victoria Bridge, Quakers Yard – Restoration Works Contract Payment, a report to Merthyr Tydfil County Borough Council.
- Our Woods in Focus, a website by the Woodland Trust.
- Taff Vale Railway entry on Wikipedia.
- Map of the Taff Vale Railway, on the GWR modellers website.
- Isambard Kingdom Brunel 200th Anniversary Exhibitions, from the Heritage In Action (Herian) website.
- Discover South Wales, a map of heritage sites from the Heritage In Action (Herian) website.
- The Taff Vale Railway – Volume 1 by John Hutton, ISBN 1-85794-249-3.
- Newsletter 110 June 2006 [PDF], from the Institution of Civil Engineers.
- Merthyr Tydfil Tramroads and their Locomotives, by Gordon Rattenbury and M. J. T. Lewis, ISBN 090146152-0.
- Pontygwaith entry on Wikipedia.
- Bringing the people of Merthyr closer to nature, the Forestry Commission press release from 29 August 2003 announcing the plan to create the Pontygwaith Nature Reserve.
- Pontygwaith on Alan George’s website.
- Cefn Glas Tunnel, on the excellent Cardiff Rail website.
- Quakers Yard and Merthyr Joint Railway, on the excellent RAILSCOT website.
- The Taff Vale Railway by D.S.M. Barrie, published on the Trackbed website.
- The Edwardsville Viaducts on Alan George’s website.
- Building Control Regulations for Merthyr County Borough Council, which includes a list of listed buildings in the borough.
- Trevithick and the Penydarren Tramroad on Deryck Lewis’ WalesRails website.
- ST0799 on the Geograph.org.uk website.
Much of the route can still be followed, though in places it is buried in industrial waste, and most of the southern part has been thoroughly disturbed in recent times by the laying of a large water main.  We will follow the route of the line is the next post.
- https://www.irsociety.co.uk/Archives/59/Penydarren.htm, accessed on 1st February 2019.
- https://www.walesrails.co.uk/trevithick.html, accessed on 1st February 2019.
- https://en.wikipedia.org/wiki/Merthyr_Tramroad, accessed on 1st February 2019.
- https://www.coflein.gov.uk/en/site/91513/details/merthyr-tramroad-penydarren-tramroad, accessed on 2nd February 2019.(cf.: Mercer, S., Trevithick and the Merthyr Tramroad, in Transactions of the Newcomen Society, xxvi (1947-9), p89-103).
- http://blog.stuartherbert.com/photography/2007/04/22/the-worlds-first-steam-engine-railway-journey, accessed on 2nd February 2019.
- https://en.wikipedia.org/wiki/Cyfarthfa_Ironworks, accessed on 2nd February 2019.
- https://www.gracesguide.co.uk/Dowlais_Ironworks, accessed on 2nd February 2019.
- https://www.gracesguide.co.uk/Penydarren_Ironworks, accessed on 2nd February 2019.
- https://www.gracesguide.co.uk/Plymouth_Ironworks, accessed on 2nd February 2019.
- http://www.ggat.org.uk/cadw/historic_landscape/Merthyr_Tydfil/English/Merthyr_019.htm, accessed on 2nd February 2019.
- http://www.himedo.net/TheHopkinThomasProject/TimeLine/Wales/Industrialization/WelshIndustry1800/MyrthyrTramroad.htm, accessed on 2nd February 2019.
- F. Trevitick; “The Life of Richard Trevithick”; quoted from … https://www.gracesguide.co.uk/Life_of_Richard_Trevithick_by_F._Trevithick:_Volume_1:_Chapter_9, accessed on 2nd February 2019.
- The Penydarren Tramroad; Notes and News; The Railway Magazine Volume 97 No. 599, March 1951, p206-208.
- E.W. Twining; The First Railway Locomotive; The Railway Magazine Volume 97 No. 599, March 1951, p197-201.
- Stuart Owen-Jones; The Penydarren Locomotive; National Museum of Wales, Cardiff; 1981. p6–10.
- http://www.bronwenthomas.co.uk/?page_id=325&main_image=352, accessed on 2nd February 2019.
- http://www.alangeorge.co.uk/plymouthironworks.htm, accessed on 2nd February 2019.
- http://www.alangeorge.co.uk/Dowlais_works.htm, accessed on 2nd February 2019.
- http://www.alangeorge.co.uk/cyfarthfa_ironworks.htm, accessed on 2nd February 2019.