Until the mid-19th century, the South Wales valleys were sparsely inhabited. The industrialisation of the Valleys occurred in two phases. First, in the second half of the 18th century, the iron industry was established on the northern edge of the Valleys, mainly by English entrepreneurs. This made South Wales the most important part of Britain for ironmaking until the middle of the 19th century. Second, from 1850 until the outbreak of the First World War, the South Wales Coalfield was developed to supply steam coal and anthracite.