The mineral resources of the upper end of the valley of the River Taff encouraged the development of iron smelting industries at Merthyr and Dowlais, and these were dominant by the first decades of the nineteenth century.

[2][page needed] Mineral extraction at Dihewyd, near Llantwit Fardre, attracted interest, and a private railway was built from pits there to the Glamorganshire Canal at Maesbach.

[3][page needed][4][page needed] Promoters associated with the Great Western Railway obtained authorisation for a trunk line from near Gloucester to Milford Haven, connecting South Wales to the GWR network and London, and the first section of their line between Chepstow and Swansea opened on 18 June 1850.

On 16 September 1845 the promoters published their intention to obtain an act of Parliament authorising their line; the Taff Vale Railway had been aware of the move (from prior public meetings) and simultaneously published its own corresponding proposals to reach the Rhondda Fawr; the far greater resources resulted in the Ely Valley scheme being abandoned immediately.

[6][page needed] In October 1856 it was announced that the Ely and Rhondda Valleys Railway was being promoted, although at first it would only build eight miles of line, from Llantrisant to Dinas (Penygraig).

In November the statutory parliamentary notice was published; the company name had been altered to the Ely Valley Railway; it was to be a broad gauge line 6+1⁄2 miles long from Llantrisant to Penrhiwfer, with two branches.

[6][page needed] The bill went to Parliament and encountered only limited opposition, and the Ely Valley Railway Act 1857 (20 & 21 Vict.

At the first formal board meeting it was decided to seek powers to build a branch to the productive Mwyndy iron ore mine, and possibly on to Brofiscin Quarry.

The primary purpose of this was to relieve the congestion at the Bute docks on the east side of Cardiff, and on the approach lines of the TVR.

In addition to the EVR converting its system to the narrow gauge, this could best be achieved by the South Wales Railway laying a third rail, to make mixed gauge track between Llantrisant and the junction for Penarth; in fact the scheme escalated to include the route as far as the Bute East Dock, mutual running powers being offered.

In fact the GWR were entirely opposed to the plan, seeing no benefit to compensate for the expense of carrying it out, and the negotiations were at an end; the EVR had wrapped up a number of secondary, but important, issues in the talks, and now these were lost as well.

But in March 1860 the magnitude of the costs involved in building the new line and converting the existing EVR system was addressed, and it was quickly seen that the whole thing was not affordable.

[6][page needed][7] The Ely Valley Railway (EVR) was not yet fully open, and thoughts now turned urgently to the working arrangements for their line.

There were two short branches: one was to Castellau, diverging north-eastward not far north of Llantrisant; the other was to Gellirhaidd, running to the west from a point not far south of Penrhiwfer.

)[6][page needed][4][page needed] At the time these discussions were proceeding, the Taff Vale Railway were encouraging the promotion of what became the Llantrisant and Taff Vale Junction Railway (L&TVJR), a line to Llantrisant from near Treforest, connecting up numerous small mines on between, and forming an intrusion into territory that the broad gauge companies considered their own.

When the Taff Vale Railway assisted it by taking part of the share issue, it was inevitable that the line would be built on the narrow gauge.

This started on 18 September 1865, when the Ely Valley Railway had finally got approval from the Board of Trade for passenger operation over the mixed gauge section.

[6][page needed] The terminus of the Gellirhaidd branch appeared ideal for a westward extension into the Ogmore Valleys, and from 1857 a number of schemes were out forward.

These were without success until 28 July 1863 when the Ely Valley Extension Railway was authorised, though in a much reduced form compared with its promoters' intentions.

To get access to a waterway, they now planned to build a line to connect to the narrow gauge Penarth Harbour, Dock and Railway company.

Notwithstanding its opposition to laying mixed gauge on the South Wales Main Line, the GWR had given a parliamentary assurance[clarification needed] that it would do so on the portion of the Ely Valley Railway to enable narrow gauge trains to run from Hendreforgan to Common Branch Junction (near Ynysmaerdy) reaching the L&TVJR there.

(It was converted to narrow gauge in May 1872 and remained detached from the Ogmore network until the completion of the Black Mill to Hendreforgan line in September 1875.

[3][page needed] The Ogmore Valley Bill was passed on the same day, authorising a connection between Blackmill and Hendreforgan, although the OVR had hoped for much wider extensions elsewhere.

[6][page needed] For some years the GWR had accepted that the broad gauge was a liability that had to be got rid of, but the latter half of the 1860s were very difficult financially, and the matter was delayed.

Now in April 1874 it negotiated a lease with the owner of Cil Ely Colliery, a short distance north of Tonyrefail, and this became a prime supplier to the GWR.

Legal argument was finely balanced, and in 1894 the EVR won its case on the basis that it was agreed that substantial infrastructure improvements—doubling much of the line (because of the density of mineral traffic), building stations etc—that the court did not have the power to demand.

[6][page needed] The section between Gellirhaidd and Penygraig was next on the agenda; there was a summit at Penrhiwfer, and as part of the work, the line would be lowered by 20 feet there.

Freight traffic fared as badly; ordinary goods business was susceptible to more flexible road lorry competition in the same way as the passenger services.

On 31 March 1952 the Llantrisant to Pontypridd passenger service was closed; this had run over part of the Ely Valley network as far as Maesaraul Junction.

The last ordinary passenger trains on the Ely Valley Railway itself, between Llantrisant and Penygraig, ran on 7 June 1958, but there was a special excursion to Porthcawl the following day.