The Symington, Biggar and Broughton Railway was a railway company in southern Scotland. It built a line connecting Biggar, and later Peebles, to the main line railway at Symington. It was taken over by the Caledonian Railway in 1861, and was completed in 1864.
The Caledonian saw it as a strategic acquisition, potentially giving it access to the Borders towns more widely, but this aim never materialised, and the line did not develop beyond its purely local status. It closed to passengers in 1950, and completely by 1966.
When the first main line between central Scotland and the English railways was being planned, the Annandale Route was favoured by many promoters; with some variations from the earliest planned route, that became the Caledonian Railway main line, nowadays part of the West Coast Main Line. The plans included a route to Edinburgh, and at first this was to leave the Glasgow to Carlisle line at Symington. This would have had the advantage of bringing Biggar into the route, but the alignment on from there was more difficult, and Glasgow to Edinburgh traffic would have had a much longer route. The Edinburgh line as actually built in 1849 left the Glasgow line at Carstairs instead.
Biggar was an important town, and the topography of the region was such that a railway connection posed no engineering difficulty. Local interests promoted a railway from Symington, on the Caledonian Railway main line. The Caledonian Railway was friendly to them, seeing their line as a possible launching point for access to the Lothian coalfields.
In 1857 plans for the line were taking definite shape, with the guidance of the engineer John Miller. The line was to be built for £30,290. At the insistence of the Caledonian, the land was to be acquired for double track, although only single track was to be laid at first: the Caledonian clearly saw the line as a future trunk route.
The Symington, Biggar and Broughton Railway was authorised by Act of Parliament on 21 May 1858. Although the continuation to Broughton was very simple, along the broad valley of the Biggar Water, it is not clear what was the intended benefit of this lengthy extension. The population of Broughton parish was under 300 and there were no notable industries.
The authorised capital of the new line was £36,000 with permitted loan capital of £12,000. The proprietors found it difficult to raise all the capital and appealed to the Caledonian Railway for help; the Caledonian subscribed £7,500 on condition that £20,000 was sourced locally, and this was done.
The line opened from Symington to Broughton on 5 November 1860, and it was worked by the Caledonian Railway.
The junction with the main line at Symington was a little distance north of the earlier station there. It is likely that arriving branch trains simply reversed from the point of junction to the station, but this was not a long term arrangement, and the passenger station was moved to the junction, opening there on 30 November 1863. The former station remained as a goods station.