The Lanarkshire and Dumbartonshire Railway was a railway company in Scotland. It was promoted independently but supported by the Caledonian Railway, and it was designed to connect Balloch (on Loch Lomond) and Dumbarton with central Glasgow, linking in heavy industry on the north bank of the River Clyde. From Dumbarton to Balloch the line would have closely duplicated an existing railway, and negotiation led to the latter being made jointly operated, and the L&DR terminated immediately east of Dumbarton, trains continuing on the joint section.
Since the twentieth century the county is now spelled Dunbartonshire, but at the time of formation of the Company, Dumbartonshire was in common use, and that is the spelling the company adopted.
The line opened progressively from 1894 to 1896. It was very successful in attracting goods traffic from heavy industry on Clydeside, and in carrying workers to and from their places of work. This was enhanced by the connection to the Glasgow Central Railway.
Heavy industry declined after 1950 and passenger and goods use of the line declined similarly, and the British Railways modernisation plan proposed electrification and upgrading of the parallel former North British Railway route, and closure of the former L&DR line. The electrification was commissioned in 1960 and the L&DR route closed in 1964 except for a short section near Dumbarton.
The Caledonian Railway was authorised in 1845 to build its trunk line from Glasgow and Edinburgh to Carlisle: that line opened in 1847 - 1848. During the lengthy period of planning the route and obtaining its Act of Parliament, the Caledonian set about gaining control of other Scottish railway companies. Many other lines were being promoted at that time of easy availability of capital, and the Caledonian quickly secured the Glasgow, Paisley and Greenock Railway and agreed leases of several other lines, mostly north of the central belt.
There was much industry in the valley of the River Leven and at Dumbarton itself, and independent promoters put forward a line that would run from Glasgow to Dumbarton and Balloch. The connection in Glasgow was to be with the Edinburgh and Glasgow Railway (E&GR) near Cowlairs, broadly following the present-day Westerton route. In 1846 the line obtained an authorising Act of Parliament; it was to be called the Caledonian and Dumbartonshire Junction Railway (C&DJR).