Formed in 1864 by the amalgamation of the Oswestry & Newtown, Newtown & Machynlleth, Llanidloes & Newtown and several other railway companies, Cambrian Railways was the largest independent railway in Wales, with a long, winding, single-track main line that extended from Whitchurch in the east to Aberystwyth and Pwllheli on the Welsh coast. In 1922, the company was amalgamated with the Great Western Railway under the provisions of the Railways Act 1921 and thereafter, the Cambrian line was worked as an integral part of the GWR system.

The present-day Cambrian main line runs from Shrewsbury to Pwllheli, a distance of 1183/4 miles, and there is an important branch to Aberystwyth. The line, which runs through spectacular mountain and coastal scenery, serves as a vital lifeline for the inhabitants of scattered towns and villages such as Welshpool, Machynlleth and Harlech, while at the same time the sinuous Cambrian route plays an important role in the Welsh tourist industry - a role that is further enhanced by the way in which this highly scenic route provides a convenient link between several of the famous Welsh ‘heritage’ railways.