Part of its route, from Croesor Junction to Porthmadog, was taken over by the Welsh Highland Railway in 1922, and upgraded to allow the operation of steam locomotives.

An initial company, the Croesor Valley Railroad was proposed under the ownership of Hugh Beaver Roberts and two other quarry proprietors.

In the meantime, slate from the Croesor Quarry was being hauled by pack mule over to the adjacent Cwm Orthin and down to the Ffestiniog Railway at Tanygrisiau, a long and dangerous journey.

The tramway continued to carry slate from the quarries along Cwm Croesor until 1944, when the last wagons were sent down the Rhosydd incline and on towards Porthmadog.

The remaining track, between Croesor and Blaen y Cwm continued in unofficial use by local farmers until the late 1950s.

Croesor Junction did not exist before 1901, when the tramway was purchased by the Portmadoc, Beddgelert and South Snowdon Railway.

The tramway continued to Pont Garreg-Hylldrem where it ran alongside the Afon Maesgwm for a short distance.

This rises another 300 feet (91 m) and ends in a winding house that straddles the tramway - this has been preserved and converted into a home.

Apart from a shallow cutting near Croesor Uchaf farm, this section of the tramway has no significant engineering features.

The next branch was just south of Croesor village and served the separate Parc Slate and Slab Quarry.

The northern line ran via a further incline to Pant Mawr Quarry, which lies at the head of Cwm Maesgwyn.

It was replaced by the line heading south, which went to Fron-Boeth Quarry which was also within Cwm Maesgwyn, and about a mile south-west of Pant Mawr.

This tramway was particularly well engineered, running for much of its distance on high embankments hundreds of feet above Cwm Croesor.

After the demise of the original Welsh Highland Railway, the stub of the tramway from Croesor village to the foot of the Blaen y Cwm incline continued in use to carry agricultural products for local farms, until the late 1950s.

The rails from this section were recovered some time in the 1960s by members of the Welsh Highland Railway preservation society and were stored at the site of Beddgelert station.