The Tanat Valley provides a useful east-west route which may have been used by the Romans, though the evidence is not conclusive. The present road from Llanfyllin through Llangynog and over the Berwyn to Bala was built as a turnpike under an act of 1769.
Ambitious proposals to use the valley for a major railway line serving the route to Ireland came to nothing, but the Tanat Valley Light Railway linking Llangynog to the Cambrian Railway at Porthywaen was authorised in 1899 and opened in 1904. Its station is now the site of the Glendower Caravan Park by the River Eirth, and the track once crossed the road to a siding serving the granite quarries. Passenger trains ran to Oswestry and minerals, coal and agricultural goods were carried.
The line closed in 1952 after a life of less than fifty years.
The corn mill by the River Eirth, accessible by public footpath from the Rhiwarth or Bala Road, ground corn into the 1930’s, but was also used from the 1920’s for generating electricity.
Power was low, but the service was maintained until a mains supply reached Llangynog in 1954.
Several cast iron water fountains can be seen around the village. Mains water did not arrive until the early 1960s.
The first council houses were built at Dolhendre, opposite the Memorial Hall, in 1948 and represented a new, higher standard of accommodation for many families. House building has continued, though not on a large scale: many of the older cottages have become holiday accommodation or second homes.