The Croesor Tramway originally carried goods traffic from around 1863. It was built on wayleaves to the order of Hugh Beaver Roberts, a solicitor of Llanrwst. Construction preceded that of the Aberystwith and Welsh Coast Railway which opened in 1867; archaeological evidence at the re-installation of Cae Pawb crossing c.2006 showed the A&WCR was built against the embankment of the tramway. The Croesor & Portmadoc Railway Company was incorporated by an act of Parliament of 5 July 1865, with a registered office in Caernarfon. This in turn was absorbed by the Portmadoc, Croesor & Beddgelert Tram Railway Company in 1879. Subsequent history is complex, the best modern account being Peter Johnson's Illustrated History of the Welsh Highland Railway. With construction of the Welsh Highland Railway in 1922, the bulk of the route was taken over and re-laid in 45lb/yd rail as far east as the first joint beyond the A4085 crossing at Carreg Hylldrem (= Ugly View Rock). Eastwards from here, the original 1860s light T-rail remained until lifted by Will Scrap (W.O. Williams, Harlech) in 1948-9. The connection with the new 1922-3 main line became known as Croesor Junction. Though there is no actual closure date for the rest of the route, most was out of use by the cessation of WHR operations in 1937. Unofficial usage apparently continued until the 1950s. It is reported that some early reclamation of items was undertaken by Ffestiniog revivalists - three solid-sided waggons from Tre Saethan became ash waggons at Boston Lodge and were later passed to Rheilffordd Llyn Tegid at Llanuwchllyn. Some of the T-rail was removed by WHR(1964)Co and moved to Beddgelert, where it was never used. (During the 2006 rebuild, this was stolen)
The seaward end of the Croesor Tramway was at Portmadoc, home of the more famous FR Co., with whose lines it connected around the harbour, a triangle in the High Street remaining until 1927. The tramway ran in a north easterly direction into the Croesor valley, initially along the Creassy Embankment, for a distance of about 5 miles where it served by inclines a number of slate quarries along the southern side of the valley - Upper and Lower Parc, Fron Boeth (= warm breast[of a hill]), Croesor (=?Crossing) and Rhosydd (= Moors). Fron Boeth had a tunnel through Moelwyn to the sunny slope of the hill, hence the name. Croesor has an impressive incline - that at Rhosydd looks actively evil, with several slate waggons on the hillside where they fell off the incline. This incline was in use until 1952 to take fuel to the pumps at Rhosydd Quarry.
The tramway opened to traffic in 1864 (possibly partially opened earlier) and survived until the 1930s, by which time regular traffic over the line had ceased. The rails remained in place until 1948-9 when the lower section was lifted by Will Scrap (as part of the dismantling of the WHR), the upper section succumbing during the 1950s or even 1960s.
The route of the tramway is still clear to see throughout most of its length and the final three miles at the south western end of the line are now being restored as part of the Welsh Highland Railway project. The route can be seen on this Map link
For a more illustrated description of the sections not being rebuilt in connection with the Welsh Highland, see the official WHR site here (external site). See this linkl for a set of photographs of the Croesor Tramway and its environs taken by Tony Statham in the early 1970s.