The North Wales Narrow Gauge Railways (NWNGR) was a railway company that planned to build a number of inter-connected 1 ft 11+1⁄2 in narrow-gauge railways across North Wales. The first two of these lines - jointly known as the "Moel Tryfan Undertaking" - were authorised by Act of Parliament 1872 and were built and opened in the 1870s. The original main line ran from Dinas Junction to Bryngwyn and opened in 1877. The second line was a branch from Tryfan Junction to South Snowdon, though shortly after opening, the company designated the Tryfan Junction to Bryngwyn section as the branch, and the Dinas Junction to South Snowdon section as the main line.

Dinas is a station on the narrow gauge Welsh Highland Railway, which was built in 1877 as the North Wales Narrow Gauge Railways Moel Tryfan Undertaking to carry dressed slate for trans-shipment to the LNWR. Passenger services ceased on 26 September 1936 until which time Dinas had been a joint station, known as Dinas Junction with the LNWR and later the LMS. In 1951, British Railways closed their part of the station but the line through the station remained open until the line from Caernarvon to Afon Wen was closed in 1964. The trackbed was subsequently developed as the Lôn Eifion tourist cycle route.