The Welsh Highland Railway, built to 600mm gauge, opened in 1923 and was formed by the merger of several much older railways: the 1863 Croesor Tramway, the 1877 North Wales Narrow Gauge Railways, and the Portmadoc, Beddgelert and South Snowdon Railway of 1902 on. The line was not a commercial success and closed in 1937.

In 1997, work started on the Welsh Highland Railway Project to restore the line. Caernarfon is now (2009) linked to Dinas Junction (nprn 91421) (narrow-gauge track has been laid on the former standard-gauge formation), Waunfawr (nprn 03562), Rhyd Ddu (nprn 405423) and Beddgelert (nprn 409177) through to Porthmadog (nprn 41441), where a link has been made with the Ffestiniog Railway (nprn 34660). The Welsh Highland Railway should not be confused with the Welsh Highland Heritage Railway (nprn 409176).

B.A.Malaws, RCAHMW, 13 July 2009.