The line was opened in 1865 to serve the Bryn Eglwys slate quarry above the village of Abergynolwyn. It used steam locomotives from the start unlike its neighbor the Corris Railway. However the Talyllyr's unusual gauge was probably adopted because of the Corris.
The line's two original steam locomotives were some of the earliest engines built for such a narrow gauge. The line carried both slate from the quarry to the wharf at Tywyn and passengers. It rarely made money and was kept going by succesive quarry owners to serve the transport needs of the isolated Bryn Eglwys quarry.
Amazingly the line survived almost unchanged through the Victorian era and both world wars. For all this time it retained the original locomotives and passenger carriages, never needing new or replacement stock. By the end of the 1940s the line had fallen into a parlous state of repair with only one working locomotive, and trains had become rare and unreliable. The line was owned by the local member of Parliament, Sir Haydn Jones, who payed for the railway's losses from his own pocket. When he died in 1949 it seemed certain the line would close.
But a group of enthusiasts decided that the Talyllyn was a unique piece of Welsh heritage and should be saved. They formed the Talyllyn Railway Preservation Society and acquired the line. In 1950 they opened the railway, thus being the first group to preserve an existing railway of any kind.
Through the 1950s the dedicated volunteers and staff members of the TRPS rebuilt the line and rescued it from its state of decay. They purchased the two remaining locomotives from the recently closed Corris Railway, and scoured the country for new carriages. Slowly the line revived.
The Talyllyn Railway is now a successful and popular tourist attraction. The two original locomotives from the 1860s still run regularly along with the Corris engines and several other steam locomotives. This delightful line continues to attract many visitors and its survivial seems assured for many years to come.