Cymmer was the second of the upper Afan valley villages to develop. It grew as an important railway junction at a point in the valley where the River Corrwg joins the River Afan.

In 1876, the area was largely rural but growth began in 1878 with the arrival of the Llynfi and Ogmore railway which linked the Afan valley via the Cymmer tunnel to the Llynfi valley with links to Maesteg, Bridgend and Cardiff.

The Rhondda Swansea Bay Railway station at Cymmer c. 1910. The building shown is the Refreshment Room which is all that remains today of the original station.

With the building of the railways, villages grew in the upper valley at Cymmer, Glyncorrwg and Aber/Blaengwynfi and with this growth the road system developed.

For over a century the coal dug from the hills and deep pits in the valley was carried by rail to industries in the lower valley at Cwmafan and Port Talbot and the local ports for export. Rail passengers could also travel to coastal towns such as Port Talbot and Swansea.