Sunderland, part of the Durham coalfield, has a coal-mining heritage that dates back centuries. At the peak in 1923, 170,000 miners were employed in County Durham alone, as labourers from all over Britain, including many from Scotland and Ireland, entered the region. As demand for coal fell after World War II, mines began to close across the region, causing mass unemployment. The last coal mine closed in 1994. The site of the last coal mine, Wearmouth Colliery, is now the Stadium of Light, and a miner's Stephenson lamp monument stands outside of the ground to honour the heritage of the site.