The railway is roughly 13+1⁄2 miles (21.7 km) long and runs from the harbour at Porthmadog to the slate mining town of Blaenau Ffestiniog, travelling through forested and mountainous terrain.

The two railways share the same track gauge and meet at Porthmadog station, with occasional trains working the entire 40-mile (64 km) route from Blaenau Ffestiniog to Caernarfon.

[5] The passing of a later act for the railway also saw cannon celebrations, but on this occasion, a fitter at Boston Lodge, who was assisting with firing, lost the fingers of one hand in an accident.

To achieve this continuous grade (about 1 in 80 for much of the way), the line followed natural contours and employed cuttings and embankments built of stone and slate blocks without mortar.

Prior to the completion in 1842 of a long tunnel through a spur in the Moelwyn Mountain, the slate trains were worked over the top via inclines (designed by Robert Stephenson), the site of which can still be seen although there are few visible remnants.

Up to six trains daily were operated in each direction and a printed timetable was published on 16 September 1856 by Charles Easton Spooner who, following his father, served as Manager and Clerk for 30 years.

Trains waited ten minutes at the intermediate stations called Tunnel Halt, Hafod y Llyn and Rhiw Goch.

Occasional confusion arises because places named Hafod y Llyn Isaf and Dinas also exist on the Welsh Highland Railway, albeit 10 miles (16 km) or more to the northwest of those on the FR.

During the late 1850s it became clear that the line was reaching its operational capacity, while the output of the Blaenau Ffestiniog slate quarries continued to rise.

[10] The original passenger coaches (some of which survive) were small four-wheeled vehicles with a very low centre of gravity, which led to them being nicknamed 'bug boxes'.

He was instrumental in getting government backing for its completion on the understanding that the FR and the WHR would be jointly managed from Porthmadog, with maintenance undertaken at Boston Lodge and with other economies of scale.

The FR continued to operate its slate traffic, a workmen's train on weekdays throughout the year and a summer tourist passenger service.

Slate traffic ceased on 1 August 1946, apart from the section from Duffws to the North Western yard through Blaenau Ffestiniog town centre, which was leased on 7 October 1946 to the quarry owners.

[13] Pegler was appointed the new company's first Chairman,[13] with the objective to operate the railway as a tourist attraction and gradually restore the line to working order.

In 1972, after the second-longest court case in British legal history,[17] the Festiniog Railway Company obtained compensation for the loss of its route.

[18] On 18 August 1954, Colonel McMullen of the Ministry of Transport, Railways Inspectorate inspected the line from Blaenau Ffestiniog to Porthmadog, accompanied by Pegler, several directors and other supporters.

Before it opened to rail traffic, the new tunnel had to be lined throughout its length with liquid cement reinforced with steel mesh in a process called 'shotcreting'.

From 26 May 1975, and over two summers, a pull and push service, officially called The Shuttle, powered by diesel locomotive Moel Hebog with carriage 110, was operated from Dduallt to Gelliwiog, to enable tourists to experience the Deviation route before the new Moelwyn Tunnel was opened.

This was followed by two public road crossings with automatic signalling, on the FR's only reverse or down gradient, to rejoin the old route in Tanygrisiau station (640 feet (195 m)), which was reopened on 24 June 1978.

The decrepit steel bridge across the Afon Barlwyd required total replacement, with timber (Karri) beams using the original abutments and piers.

One major task near Tanygrisiau was the responsibility of Gwynedd County Council, which had at some time after 1955 taken advantage of the absence of trains to demolish what was probably Britain's lowest road under railway bridge.

[citation needed] In early 1980, therefore, they replaced Dolrhedyn bridge and even managed to give it a few inches extra headroom for road vehicles.

The new joint station with British Rail at Blaenau Ffestiniog was officially opened on 30 April 1983 by George Thomas, Speaker of the House of Commons, who unveiled a plaque that records his visit.

Pegler, who remained fully involved with the railway until his death in 2012 as President, was appointed OBE in the 2006 New Year Honours in recognition of his contribution.

This was not guaranteed, as pressure from various groups who objected to the rebuilding of the railway was significant and it was the stated intention of the council to apply for an abandonment order on gaining the track bed.

By 2010, the tracks of the WHR and Ffestiniog Railway had been reconnected at Harbour Station, linking Caernarfon to Porthmadog and passenger services started in 2011.

[35] At Porthmadog, the original line came via the streets and across the Britannia bridge from the 1836 terminus at the northernmost end of the Welsh Slate Company's Wharf where the FR officially started.

By the end of the 1970s, the passing loops were at Minffordd, Rhiw Goch, Tan-y-Bwlch and Dduallt, and an intensive service was run in the peak summer seasons (although there were empty "slots" in the timetable which could be used by works trains).

In June 2002, the loop was once again used to run trains around as part of the 2002 Gala to celebrate the twentieth anniversary of the restoration of services to Blaenau Ffestiniog.

The intended platform starter signals (posts, brackets and arms) have been recovered and some are now in use on the Isle of Man Railway, whilst others are destined for the resignalling of Harbour Station.