Cardiff in making iron and later steel, brought to the sea by packhorse from Merthyr Tydfil. This was first achieved by the construction of a long canal from Merthyr (510 feet above sea-level) to the Taff Estuary at Cardiff. Eventually the Taff Vale Railway replaced the canal barges and massive marshalling yards sprang up as new docks were developed in Cardiff – all prompted by the soaring worldwide demand for coal from the South Wales valleys. At its peak, Cardiff's port area, known as Tiger Bay, became the busiest port in the world and – for some time – the world's
Cardiff Bay of hours each side of high water but now provides 24-hour access through three locks. Cardiff Bay played a major part in Cardiff’s development by being the means of exporting coal from the South Wales Valleys to the rest of the world, helping to power the industrial age. The coal mining industry helped fund the building of Cardiff into the Capital city of Wales and helped the Third Marquis of Bute, who owned the docks, become the richest man in the world at the time. As Cardiff exports grew, so did its population; dockworkers and sailors from across the world