20. Blaenavon Ironworks. "The modern history of Wales starts in the 19th century when South Wales became heavily industrialised with ironworks; this, along with the spread of coal mining ... led to an increase in population. The social effects of industrialisation resulted in armed uprisings against the mainly English owners. Socialism developed in South Wales in the latter part of the century, accompanied by the increasing politicisation of religious Nonconformism."