Glasgow & South Western Railway

The Glasgow and South Western Railway (GSWR or 'Sou'west') was a Scottish pre-grouping railway formed on 28 October 1850 by the amalgamation of the Glasgow, Paisley, Kilmarnock & Ayr Railway and the Glasgow, Dumfries & Carlisle Railway. Its system covered south-west Scotland, the Anglo-Scottish route via Kilmarnock, Dumfries and Carlisle (a long-running rival of the Caledonian's main line through Beattock); the Ayrshire coast lines to Ardrossan, Largs and Stranraer; and the steamer-train services to Arran, Bute and Ireland.

Locomotive engineering was conducted at the company's Kilmarnock Works under successive Locomotive Superintendents, Patrick Stirling (1853–1866), James Stirling (1866–1878), Hugh Smellie (1878–1890), James Manson (1890–1911) and Peter Drummond (1912–1918). The 'Sou'west' was always the smaller and less prosperous of the two main Scottish-English trunk routes; Drummond's freer hand at Kilmarnock produced sound mixed-traffic engines but no large express designs.

At Grouping on 1 January 1923 the GSWR became part of the LMS, in whose Scottish Area the company's blue express engines were rapidly displaced by Caledonian-derived practice.