The route between Ayr and Stranraer comprises of five stations – Ayr, Maybole, Girvan, Barrhill and Stranraer.

Opened in 1854 the Ayr and Dalmellington Railway was built to serve the iron works and coal mines in the Doon Valley. South of Dalmellington Junction, formerly called Maybole Junction, was the five and a quarter mile Ayr & Maybole Junction Railway which opened in 1856 and terminated to the north of the existing station at Maybole.

Four years later, the Maybole & Girvan Railway extended the line to a small terminus close to the harbour at Girvan. From the beginning, both railways were operated by the Glasgow & South West Railway (G&SWR) and by 1871 G&SWR had full control of both companies.

In 1862 as part of a deal between the Government and Royal Mail, a railway opened between Castle Douglas and Portpatrick. This was done to restore a ferry link that had operated between 1662 and 1849 across the short channel crossing from Scotland to Donaghadee in County Down. Later, Stranraer and Larne became the terminal points of the North Channel ferry crossing.

The Portpatrick Railway was opened in October 1862 and became known as the ‘Port Road’ and provided the only railway link between Glasgow and Belfast. Within Scotland, this involved a journey down either the modern-day West Coast Main Line – then operated by Caledonian Railway – to Lockerbie and on to Dumfries. The other option was to head to Dumfries, via Cumnock, on the Glasgow & South West Railway, a distance of at least 155 miles depending on the chosen route. It was actually quicker to board a steamer at Ardrossan and sail to Belfast than to follow the circuitous route via Dumfries!

Finally in 1877 the missing link was opened. This was the Girvan & Portpatrick Junction Railway, operated by G&SWR, and ran through the villages of Pinmore, Pinwherry and Barrhill to join Portpatrick Railway at Challoch Junction. It was eventually acquired by G&SWR in 1892. In 1923, The London, Midland & Scottish Railway took control before nationalisation under British Transport Commission in 1948. British Rail then took charge in 1963 until privatisation in 1994.

Under franchising, the line became part of the ScotRail franchise won by National Express in 1997. In 2004, First Group won the right to operate the ScotRail franchise and in 2014 Abellio/ScotRail won the tender to operate the line.