 Nant Gwernol station was opened in 1976; before 1976 this upper part of the line had only been used for goods services.The station is built on the site of the former marshalling yard at the foot of the Alltwyllt incline, which was the first of the two inclines between the Talyllyn Railway and the Bryn Eglwys slate quarry.This site was chosen as the terminus of the passenger line, as it was the limit of locomotive working.