As the Industrial Revolution took off, a series of works were built along the Tawe river from 1720 onwards and a series of mines were opened. Initially, the smelting works concentrated on copper. Coal was brought down to them by waggonways and tramways; copper ore was brought on ships which could sail right up to the works; the resulting copper was exported out again. Swansea had become ""Copperopolis"", processing at its peak as much as 70% of the world’s copper, and the lower Tawe valley became a mass of industry.