Merthyr Tydfil () grew around the Dowlais Ironworks which was founded to exploit the locally abundant seams of iron ore, and in time it became the largest iron-producing town in the world. New coal mines were sunk nearby to feed the furnaces and in time produced coal for export. By the 1831 census, the population of Merthyr was 60,000—more at that time than Cardiff, Swansea and Newport combined—and its industries included coal mines, iron works, cable factory, engine sheds and sidings and many others. The town was also the birthplace of Joseph Parry, composer of the song "Myfanwy".