The Glasgow, Dumbarton and Helensburgh Railway was independently sponsored to build along the north of the River Clyde. It opened in 1858, joining with an earlier local line serving Balloch. Both were taken over by the powerful North British Railway in 1865, and for some time the line was the main route in the area. As industry developed other lines were opened to serve it, and the line formed the core of a network in the area.
The line was electrified as part of a modernisation scheme in 1960, and it continues today as the trunk of the North Clyde network west of Glasgow.
The communities of Dumbarton and Helensburgh were important staging points on the road from Glasgow to the western seaboard of Scotland, and were well served by small boats on the River Clyde.
Most of the first railways in Scotland were the coal railways, designed to convey coal or other minerals from a pit to a port or a canal for onward conveyance. Generally these lines used horse traction and were short.
In 1842 the Edinburgh and Glasgow Railway (E&GR) started its operations, and showed what an inter-city railway could do, carrying passengers and goods over a longer distance. Towns served by the new railway immediately felt the advantage, as the necessities of life, particularly coal and line for farm use, became much cheaper, and the transport to market of locally manufactured goods was also immeasurably improved.
The notion of long distance railways, and a network, took hold of the public imagination, and the easily available money of the 1840s led to a frenzy of Scottish railway promotion. Intrinsic in this was the question of how the cities of central Scotland might best be linked with the emerging English railway network. This culminated in the authorisation of a large number of Scottish lines in 1844 - 1845.
Those railways, notably the North British Railway, the Caledonian Railway and the Glasgow and South Western Railway, had their own priorities, which in most cases was to consolidate the area in which they were dominant. At first the north bank of the Clyde was left to the river boats.