The Ironbridge is an amazing early example of Social Media. In the 1770's Abraham Darby figured out how to mass produce cast iron much cheaper than anyone else. To advertise his process he built a huge bridge across the River Severn in a deep gorge. The bridge was opened January 1st 1779 and has spanned the River since. Many bridges upstream and downstream were distroyed by floods, the Ironbridge is still standing. It became such an important crossing that a town grew up around it, which is also called Ironbridge. At the time, this area was the center of the industrial revolution, silicon valley of its day. Over the years industry moved to Birmingham and Coventry, leaving behind this wonderful testament to ingenuity. The bridge isn't bolted, nor welded, not even riveted together, it is basically woodworking joints, dovetails and wedges. No one had used iron so no one knew how to join the pieces, so they used what they knew, woodworking joinery.