Chronology for Rhondda Valley Branches
| / | / | 1800 | Rhondda Valley Branches (Taff Vale Railway) | Extension to Maerdy opened by buying a private line from Ferndale to Maerdy. |
| / | / | 1849 | Rhondda Valley Branches (Taff Vale Railway) | Extended from Porth to Dinas. |
| / | 12/ | 1849 | Rhondda Valley Branches (Taff Vale Railway) | Extended from Porth to Ynyshir. |
| / | / | 1856 | Rhondda Valley Branches (Taff Vale Railway) | Extension to Ferndale opened. |
| 7/ | 8/ | 1856 | Rhondda Valley Branches (Taff Vale Railway) | Extension to Treherbert opened. |
| 4/ | 2/ | 1861 | Rhondda Valley Branches (Taff Vale Railway) | Pontypridd to Ystrad opened to passengers. |
| / | / | 1863 | Pwllyrhebog Branch, Rhondda Valley Branches (Taff Vale Railway) | Opened from Tonypandy to Blaenclydach Goods. The line was worked by specially designed 0-6-0 tank engines, of 1884, which were safe to work on the incline. The incline was also cable operated. |
| 7/ | 1/ | 1863 | Rhondda Valley Branches (Taff Vale Railway) | Ystrad to Treherbert opened to passengers. |
| / | 6/ | 1876 | Rhondda Valley Branches (Taff Vale Railway) | Porth to Maerdy opened to passengers. |
| / | / | 1889 | Pwllyrhebog Branch, Rhondda Valley Branches (Taff Vale Railway) | Extended to Pwllrhebog Colliery by buying its railway. |
| / | / | 1900 | Rhondda Valley Branches (Taff Vale Railway) | Introduce steam railcars to compete with buses. |
| 1/ | 7/ | 1951 | Pwllyrhebog Branch, Rhondda Valley Branches (Taff Vale Railway) | Closed. |
| 15/ | 6/ | 1964 | Rhondda Valley Branches (Taff Vale Railway) | Porth to Maerdy closed to passengers and line singled. |
| / | / | 1973 | Rhondda Valley Branches (Taff Vale Railway) | Singled from Cwmparc to Treherbert. |
| / | / | 1981 | Rhondda Valley Branches (Taff Vale Railway) | Porth to Cwmparc singled. |