Ironbridge is a village located on the banks of the river Severn, in Telford, Shropshire. Set in Ironbridge Gorge, originally the Severn Gorge, it now takes it name from the Iron Bridge, built in 1779, which crosses the gorge.
Ironbridge Gorge is the place that changed the world. Known as the Birthplace of the Industrial Revolution, as it is where Abraham Darby I perfected the technique of smelting iron with coke, allowing much cheaper production of iron. The grandson of the first Abraham Darby, Abraham Darby III, built the famous bridge, designed by Thomas Farnolls Pritchard, to cross the gorge. Construction began in 1779 and the bridge opened on New Year's Day 1781. It was the first arch bridge in the world to be made out of cast iron.
In the early eighteenth century the only way to cross the Severn Gorge was by ferry. However, with the growing industries, the area needed a reliable crossing. Shares were issued to raise the £3,200 required, and Darby agreed to fund any overspend. This wound up costing Darby and his company nearly £3,000. The bridge was far more expensive than first envisaged and Darby bore most of the cost over-run, and was in debt for the rest of his short life.
As this was the first of its kind, with no precedent, it was natural to base construction on carpentry. Each part of the frame was cast separately. Bolts were used to fasten the half-ribs together at the crown of the arch. Some parts were large, as they had to be, the bridge had to span 100 feet, rising to about 60 feet above the river. The largest parts were the half-ribs, each about 70 ft long and weighing 5.25 tons. The bridge comprises more than 800 castings of 12 basic types, using mortise and tenon and blind dovetail joints to join them together. The smaller parts were cast using wooden patterns, the large ribs were cast freely into excavated moulds in the casting sand.
After a few years, cracks were appearing in the masonry abutments, caused by ground movement. Some of the present-day cracks in the cast iron may date from this time, although others are probably casting cracks. By 1802, the southern stone abutment had to be demolished, then replaced by iron arches. Many of the cracks visible today in the bridge have been left untouched. The bridge was over designed, and later bridges built used much less cast iron.
The bridge was pedestrianised in 1934, but tolls were still were collected until 1950.