As the mines and other industries rapidly expanded throughout the coalfield, nearby towns also expanded to meet the demand for labour. In the first half of the nineteenth century, the development of ironworks saw the population of Merthyr Tydfil, in the northern part of the coalfield, increase from 7,700 in 1801 to 49,794 in 1861, making it the largest town in Wales. As Cardiff and other ports in South Wales grew to meet the demands for exporting iron, steel and coal in the later part of the nineteenth century, valleys that had previously been sparsely inhabited suddenly increased in population. The Rhondda valley grew from less than a thousand people in 1851 to more than 150,000 in 1911.