The line's core purpose was to carry iron ore northwards from mines on the Brendon Hills to Watchet harbour on the Bristol Channel.

The line included a massive rope-worked inclined plane[7][8][9][10] 3,272 feet (997 m) long to bring the ore down a 770-foot (230 m) vertical interval on a 1-in-4 (25%) gradient.

There were stations on the sections of the line below the inclined plane at Watchet, Washford, Roadwater and Comberow; trains also called by request at stopping places at Torre and Clitsome.

Several different locomotives were used during the operation of the line, including 0-4-0ST "Box" tanks built by Neilson and Company and larger Sharp, Stewart 0-6-0STs.

[11] At an altitude of over 1,000 feet (300 m) and remote from usable roads, the deposits needed a form of transport to get the ore to South Wales.

Thomas Brown (1803–1884), managing partner of the Ebbw Vale company, realised that a railway to the quay at Watchet was the solution.

[12] The Ebbw Vale proprietors formed the West Somerset Mineral Railway for the purpose, and obtained Parliamentary authority on 16 July 1855 for a standard gauge 1,435 mm (4 ft 8+1⁄2 in) line from Watchet Quay to Heath Poult (or "Exton").

A rise in altitude of 803 feet (245 m)[24] to reach the mines was accomplished by a gravity worked incline, 0.75 miles (1.21 km) long, on a gradient of 1 in 4 (25%).

Ore was brought down the incline while it was being completed, from 31 May 1858, and it was not fully finished until March 1861,[27] when two 18-foot (5.5 m) diameter winding drums were installed on a single axle, located below the track, at Brendon Hill.

[28][15] In the same year an advertisement was placed in the Somerset County Gazette announcing that "coal, culm, lime corn, flour, manure, building materials and other goods" would be carried on the railway at reduced rates.

[29] Although the outward terminal of the line was to be the quay at Watchet, the west pier had been practically unusable for some considerable time, and boats were beached and loaded direct from carts brought on to the foreshore.

In 1864 the Board decided to seek powers to extend the railway beyond Gupworthy to workings in Joyce's Cleeve in the Quarme Valley.

[38] At the top of the incline the line ran along the Brendon ridge in both directions, eastward to Raleigh's Cross and westward to a heathland terminus named after the nearby village of Gupworthy.

[53][54] The line operated successfully and settlements of people attracted to the area by the prospect of employment in the mines grew around the Brendon ridge.

A second-hand Robey[62] semi-portable steam engine was installed at the head of the incline to power the drums, hauling wagons up in the absence of a regular downhill flow.

[57] Closing the mines not only had the immediate effect of ending the line's core traffic, it led to depopulation of the villages south of the incline, reducing further what was in any event "trifling" income from goods and passengers.

[65][66][67] The lower section of the line and the incline were brought back into use, but the Gupworthy extension from Brendon Hill remained closed.

[69][70] and a new 2 ft (610 mm) gauge tramway was built from Brendon Hill to the Colton Iron Mine's western adit.

This was at a lower altitude than Brendon Hill, so the tramway had to ascend from the mine on a new double track incline worked by a stationary steam engine using a two-cylinder winch drive with twin drums.

[71][72][73] The tramway, which included a wooden viaduct,[74][75] ran nearly 2 miles (3.2 km) to Brendon Hill, where the ore was tipped into standard gauge wagons[76][77] which were lowered down the incline and hauled to Watchet.

The Colton investment sought to give an income while the Syndicates' greater hope was developed — a new iron mine near the foot of the incline at Timwood.

The concept was to mine laterally into the foot of the hill rather than downwards from the top, which inevitably involved significant costs in pumping water, raising ore and lowering it again.

[80] Traffic levels on the WSMR in his period give a clear indication of the paucity of output: "Generally the locomotive made one visit to Comberow and back daily, but on some days it did not leave its shed.

Angus, an Australian inventor, brought two locomotives onto the lower section of the line to test and demonstrate an automatic signal warning device.

In September 1918 the Timber Supply Department of the Board of Trade applied for and were granted permission to lay a light railway on the lower trackbed and to use either Washford or Roadwater station buildings.

[104] Two tender locomotives were used to demonstrate the Angus automatic train control equipment; they had originally been West Midland Railway 2-4-0s numbers 103 and 104.

[130] The shed stood east of the line in the Whitehall area, a short distance south of Watchet (WSMR) station.

The 2 ft (610 mm) Colton Tramway was worked by two small locomotives, both of which faced the main line at Brendon Hill.

[151][152] The line continued west to Gupworthy with modest earthworks; these are still visible, together with some bridge abutments, where minor roads cross the alignment.

[12] The Carnarvon New Pit iron mine and a section of the mineral railway track-bed adjacent to it has been scheduled as an ancient monument.