Ironbridge, structure that is generally considered the first cast iron bridge, spanning the River Severn at Ironbridge, near Coalbrookdale, in Shropshire, England. It is now a British national monument, and the bridge, together with the town of Ironbridge and the Ironbridge Gorge, forms the UNESCO Ironbridge Gorge World Heritage site.
The bridge’s semicircular arch spans 30.6 metres (100.5 feet) and has five arch ribs, each cast in two halves. Designed by Abraham Darby or Thomas Pritchard, the bridge was erected by Darby in 1777–79. (A similar bridge had been cast in France a few years earlier but not erected.) The bridge collected its first tolls in 1781 and is still used for pedestrian traffic, despite a slight humping of the arch.