This line connected Bala westwards to Ffestiniog and Blaenau Ffestiniog. A short portion of the line remains in use as the terminus of the Conwy Valley line in Blaenau Ffestiniog, and an out of use portion runs as far south as Trawsfynydd beyond which it is closed and lifted.
The line originally reached Ffestiniog in 1882 from the east and was extended on in 1883, after the Festiniog and Blaenau Railway was converted to standard gauge, to Blaenau Ffestiniog.
It closed to passengers on January the 2nd, 1960 and to freight on January the 27th 1961. A new link (by a BTC Act of 1959) to the north was made with the Conwy Valley line (the former Blaenau Festiniog Branch (London and North Western Railway)) on the 20th of April 1964 to provide rail access to the former site of Trawsfynydd Lake Halt where a depot for the nearby nuclear power station was built.
In 1982 the site of the terminus in Blaenau Ffestiniog became the terminus of the Conwy Valley line when its terminus closed and a new station opened on the site of the former terminus of the Bala line.
In 1998 the line south of Blaenau Ffestiniog (excluded) closed to traffic but has been retained.