Eginawc, the easternmost Cantref of Ystrad Tywi. The area was noted for its valuable land and was highly contested by the early Welsh kingdoms. During the Viking Age, the mouth of the Tawe became a focus for trade, and a trade post may have been founded sometime between the 9th and 11th centuries. When the Normans took control of the settlement, they built Swansea Castle and minted coins bearing the names Swensi, Sweni and Svenshi . The first charter was granted sometime between 1158 and 1184 by William de Newburgh, 3rd Earl of Warwick. This charter contains the earliest reference in English to Sweynesse and gave it the status of a borough, granting the townsmen (called burgesses) certain rights to develop the area. In 1215 King John granted a second charter, in which the name appears as Sweyneshe. A town seal which is believed to date from this period names the town as Sweyse. Following the Norman conquest, a marcher lordship was granted by Henry I under the title of Gower. It included land around Swansea Bay as far as the River Tawe, the manor of Kilvey beyond the Tawe, and the peninsula itself. Swansea was designated chief town of the lordship and received a borough charter at some point between 1158 and 1184 (and a more elaborate one in 1304). Industrial Revolution From the early 1700s to the late 1800s, Swansea was the world's leading copper-smelting area. Numerous smelters along the River Tawe received copper and other metal ores shipped from Cornwall and Devon, as well as from North and South America, Africa, and Australia. The industry declined severely in the late 1800s, and none of the smelters is now active. The port of Swansea initially traded in wine, hides, wool, cloth and later in coal. After the invention of the reverbatory furnace in the late 1600s, copper smelting was able to use coal rather than more-expensive charcoal. At the same time, the mines of Cornwall were increasing copper production. Swansea became the ideal place to smelt the Cornish copper ores, being close to the coalfields of South Wales and having an excellent port to receive ships carrying Cornish copper ore. Because each ton of copper ore smelted used about three tons of coal, it was more economical to ship the copper ore to Wales rather than send the coal to Cornwall. The first copper smelter at Swansea was