Incorporated on 22 July 1861 to build a line north from Aberystwyth to Pwllheli via Tywyn, Barmouth and Porthmadoc, the railway was to bridge the Dyfi estuary and connect with the Newtown and Machynlleth Railway at Machynlleth. An Act of 27 July 1862 gave powers to build from Barmouth to Dolgellau. The Machynlleth-Aberystwyth section (21 miles) was begun first, but firm foundations for the Dyfi bridge could not be found; the crossing was abandoned and the line built along the estury shore instead. It opened in stages (Machynlleth-Borth 1 July 1863, to Aberystwyth 23 June 1864). The line north opened throughout on 10 October 1867, but before it was finished the company had amalgamated with the CambR with effect from 5 August 1866.