steam coal gave rise to the rapid population growth. The development began with the start-up of the Bute Merthyr colliery in Treherbert in 1855. In the Rhondda Fach, the first coal was mined in 1862 at Ferndale. The Taff Vale Railway reached Treherbert in 1856. Collieries then rapidly developed along the valley, with the lower part of the valley developing last because of the deeper pits required to find the steam coal in that area. By the end of the century, mining villages formed an almost continuous urban strip along both valley floors, with coal mining and its ancillary trades virtually the sole industry. The majority of the incomers came from West Wales, particularly Carmarthenshire and Ceredigion and spoke Welsh. Over 70% of the population of the parish was Welsh-speaking in 1891. In 1877, the Hamlet of Rhigos was made a separate civil parish, and the remainder of Ystradyfodwg, together with the adjoining Rhondda valley portions of the parishes of Llanwonno and Llantrisant, became the urban sanitary district of Ystradyfodwg. This extended district became Ystradyfodwg Civil Parish and Urban District in 1894, and was renamed Rhondda Civil Parish and Urban District in 1897. See Rhondda (district). See also 1894 Ystradyfodwg Urban District Council election References External links Ystradyfodwg on Genuki Former subdivisions of Wales History of Glamorgan History of Rhondda Cynon Taf