established in 1717, followed by many more. Once smelting was established, the smelters began receiving high-grade ore and ore concentrates from around the world. More coal mines opened to meet demand from northeast Gower to Clyne and Llangyfelach. In the 1850s Swansea had more than 600 furnaces, and a fleet of 500 oceangoing ships carrying out Welsh coal and bringing back metal ore from around the world. At that time most of the copper matte produced in the United States was sent to Swansea for refining. Smelters also processed arsenic, zinc, tin, and other metals. Nearby factories produced tinplate and pottery. The Swansea smelters became so adept at recovering gold and silver from complex ores that in the 1800s they received ore concentrates from the United States, for example from Arizona in the 1850s, and Colorado in the 1860s. The city expanded rapidly in the 18th and 19th centuries, and was termed "Copperopolis". From the late 17th century to 1801, Swansea's population grew by 500%—the first official census (in 1841) indicated that, with 6,099 inhabitants, Swansea had become significantly larger than Glamorgan's county town, Cardiff, and was the second most populous town in Wales behind Merthyr Tydfil (which had a population of 7,705). However, the census understated Swansea's true size, as much of the built-up area lay outside the contemporary boundaries of the borough; the total population was actually 10,117. Swansea's population was later overtaken by Merthyr in 1821 and by Cardiff in 1881, although in the latter year Swansea once again surpassed Merthyr. Much of Swansea's growth was due to migration from within and beyond Wales—in 1881 more than a third of the borough's population had been born outside Swansea and Glamorgan, and just under a quarter outside Wales. Copper smelting at Swansea declined in the late 1800s for a number of reasons. Copper mining in Cornwall declined. The price of copper dropped from £112 in 1860 to £35 in the 1890s. In the early 1900s, mining shifted to lower-grade copper deposits in North and South America, and the lower-grade ore could not support transportation to Swansea. The Swansea and Mumbles Railway was built in 1804 to move limestone from the quarries of Mumbles and coal from the Clyne valley to Swansea and to the markets beyond. It carried the world's first fare-paying rail passengers on the day the British Parliament abolished the transportation of slaves from Africa. It