West Midlands (region) - The cast iron Iron Bridge at Coalbrookdale, opened in January 1781 and was the first large-scale object made out of cast iron; but cast iron is not reliably strong due to impurities. Wrought iron, where the carbon is hammered to remove to carbon and impurities is much stronger; the first large-scale wrought iron bridge was the Britannia Bridge over the Menai Strait, only possible due to its innovative box girder design by Robert Stephenson