It was a relatively long line, built for the construction and subsequent maintenance of a 15-mile-long (24-kilometre) tunnel from Loch Treig to a factory near Fort William in Scotland.

This requires large amounts of electricity to perform the electrolysis, and the first factory in the United Kingdom where this was carried out was opened at Foyers, on the shores of Loch Ness, in 1896.

It was owned by the British Aluminium Company, and as world demand for the metal rose rapidly, a second factory was opened at Kinlochleven in 1908, using water power provided by the Blackwater Reservoir.

With demand continuing to rise, plans were drawn up in 1918 to extend the Kinlochleven plant, but these met with strong opposition.

In particular, Kinlochleven did not have sufficient spare space to build housing for the number of workers needed by the enlarged factory, and the private bill lodged with Parliament to promote the scheme was withdrawn.

[2] A revised scheme was proposed in 1921, still using water from Loch Treig, but instead of routing it to Kinlochleven, it would be carried through a 15-mile (24 km) tunnel to a works built on the eastern edge of Fort William.

A 1,400-foot (430 m) unlined tunnel was constructed, which fed water into a 475-foot (145 m) pipeline, providing 100 feet (30 m) of head to the three three-phase generators.

Some 1.5 miles (2.4 km) of narrow gauge railway were constructed to link the Monessie work sites together.

It was about 0.5 miles (0.8 km) long, and a 3 ft (914 mm) gauge railway linked it to the site of the aluminium factory, known as 'base camp' in the early stages of the project.

The railway was laid at an average gradient of 1 in 35 to a point 3.25 miles (5.2 km) from Base Camp, where a junction served a branch that ran back along the hillside to the adit.

The teams consisted of six to ten men, working with pickaxes and shovels, and they were able to level 30 to 100 yards (27 to 91 m) of the formation each day.

[6] The Pier Railway was always intended as a permanent feature, and was laid with heavy duty rails, weighing 60 pounds per yard (30 kg/m).

[8] The Upper Works Railway was laid with lighter rails, weighing 30 to 35 pounds per yard (15 to 17 kg/m), as it was intended to be a temporary feature.

Large teams of men were employed to build trestle bridges using local timber over the many streams which crossed the path of the railway.

It was mostly single track, but emerged into the open air at adits and the portals, where sidings were built to allow shunting of full and empty spoil wagons.

The principal location on the railway was the factory area (or 'Base Camp' prior to its opening), where there were various facilities such as a locomotive and speeder shed.

The bridge that crossed the West Highland Railway is still extant, although the embankment leading to it on the eastern side was removed in 2019.

It had been the intention that the permanent pier railway would be worked by electric traction, supplied by overhead lines, but this was never implemented.

The Upper Works Railway was by far the longest part of the rail system, running for some 19 miles (31 km) from base camp to the valve shafts located by Loch Treig.

A short 2 ft (610 mm) gauge incline ran upwards from the portals to the surge shaft.

[17] Most of the bridges on the line were originally timber trestles but all were subsequently rebuilt in steel using suitable scrap material from the factory.

In October 1971, heavy rainfall caused part of the Upper Works Railway to be washed away, leaving a gap of around 70 ft (20 m) in the track.

Brazil class 0-4-2ST, 'Sir Murray Morrison', went to the Hampshire Narrow Gauge Society, where much of it was reused as spare parts, while the funnel, cab and chassis were subsequently rebuilt by Alan Keef.

The rebuilt locomotive was named 'Dromod', and worked on the Cavan and Leitrim Railway at Dromod from 1994, but in 2019 was at Fowler and Co in Cumbria for rebuilding.