The railway links many of the same places as the road. Many more places were served by both the railway and the road before three new road bridges were built: across the Moray Firth (between Inverness and the Black Isle), the Cromarty Firth and the Dornoch Firth. The railway is now, in many places, a long way inland from the route of the A9.
The railway loops inland from Tain to Lairg, which has never been on the A9, a diversion intended at the time of construction to open the centre of Sutherland to trade. The route then returns to the coast at Golspie. For many years there have been proposals to bypass this Lairg loop with a line across the Dornoch Firth, linking Tain (via Dornoch) more directly with Golspie. This would involve building a new bridge over the Firth, or making dual-purpose the bridge which now carries just the A9. At present there seems to be little real prospect of such plans being implemented.
Beyond Golspie, the railway continues along the coast as far as Helmsdale, then inland up the Strath of Kildonan and then across the Flow Country to Halkirk and back to the east coast at Wick. At Georgemas Junction near Halkirk, there is a branch to Thurso.
In latter years the service was provided by Class 37 locomotive and Mark 1 rolling stock. These were replaced by Class 156 units.
Since 2004 this service has been operated exclusively using Class 158 DMUs as two coach trains. Prior to this some Class 156 units were used and trains were split at Georgemas Junction one half going to Thurso to other to Wick.
|Places||Grid references||Other Notes|
|Muir of Ord|
|Dingwall||The Kyle of Lochalsh Line diverges at Dingwall.|
|Fearn||This small village (full name Hill of Fearn, ) is about two kilometres (one mile) east of the station. This station also benefits the Seaboard Villages.|
|Ardgay||When first built, and for many years afterwards, Ardgay station was named for the nearby village of Bonar Bridge.|
|Lairg||Lairg station is over two kilometres (one mile) south of this small town ().|
|Georgemas Junction railway station||In the past, passenger services divided at Georgemas Junction, part of the train going to Thurso, the other to Wick. In the 1990s this practice was changed. Trains now run to Georgemas, reverse to reach Thurso, and then return through Georgemas a second time before continuing to Wick.|
The line was built in several stages:-
Much of the work was done by the Inverness-based Highland Railway company or, when completed, taken over by that company. In 1923 the Highland Railway was grouped into the London, Midland and Scottish Railway, under the Railways Act of 1921.
Like railway lines generally in Britain the line was not a product of any strategic plan, but was an ad hoc development, facilitated by Private Acts of Parliament (which were themselves a significant expense for developers) and dependent on cooperation between companies and individuals, each with their own private vested interests. The line did become strategically important during World War I and World War II as part of a supply route for Scapa Flow, Orkney: Jellicoe's Express linked Thurso directly with London (Euston) and Portsmouth.
That the line extends beyond Ardgay in the county of Ross and Cromarty is due, to a large extent, to the railway enthusiasm (some might say madness) of the 3rd Duke of Sutherland. The duke did realise his dream of being able to run his own private train to and from his own station at Dunrobin Castle.
The duke's enthusiasm took the line as far as Gartymore, a little south of Helmsdale, in the county of Sutherland, but this development was more of a financial liability than an asset: the long-term viability of the line then depended on a Caithness willingness, not least from the 17th Earl of Caithness, to link the line to the population centres of Wick and Thurso.
North of Helsmdale the line was built by the Sutherland and Caithness Railway. Turning inland it reaches Forsinard in the Flow Country. The building of the line through the Flow Country - one of the least densely populated parts of Scotland - was to avoid the Berriedale Braes. North of Helmsdale as far as Lybster, it would have been impractical to have built a railway without massive civil engineering projects. Thus coastal villages such as Latheron and Lybster are not served by the line.
In 1902, under the provisions of the Light Railways Act of 1896, the standard gauge Wick and Lybster Railway was built along the east coast of Caithness, running south from Wick to Lybster. This line was never profitable, and it closed in 1944.