There had been ironworks in this valley long before Darby. At the Dissolution of the Monasteries in 1540, the lands here belonged to Much Wenlock Priory and contained a bloom smithy called "Caldebroke Smithy." John Brooke, the local landowner from about 1572, developed coal mining on a serious scale, and his son Sir Basil Brooke was a significant industrialist who in 1615 acquired interest in the patent for the cementation process of steel-making. Brooke's estate was sequestrated during the Civil War, but the works continued. By the 1680s the blast furnace was operated by Lawrence Wellington, then by Shadrach Fox - who may have experimented with coal-smelting iron and supplied round shot and grenade shells to the Board of Ordnance during the Nine Years War. In April 1703 Fox's furnace blew up. It sat derelict for six years until Darby arrived.

The breakthrough was geology and craft together. Coalbrookdale sits on a particular seam of low-sulphur "coking coal" easily mined from drift workings in the valley sides - cleaner than most British coals and therefore producing coke clean enough to make good iron. Darby seems to have learned coke-smelting at the Bristol brassworks, where copper alloys had been melted with coke for years. He rebuilt the old furnace, lit it with coke in 1709, and produced iron at scale. The next year he renewed his lease and brought in partners - John Chamberlain and Thomas Baylies. A second furnace went up in 1715. Darby died young at Madeley Court in 1717, but the business survived: it passed to a partnership led by Bristol Quaker Thomas Goldney II, managed by Richard Ford, with Darby's son Abraham Darby II brought in as assistant manager when he was old enough. The Quaker network ran the early Industrial Revolution at Coalbrookdale much the way it ran railways and chocolate later: through trust, marriage, and intergenerational patience.

The Old Furnace - the very one Darby rebuilt in 1709 - still survives. It is now under a protective building erected in 1981, but the asymmetrical interior profile remains clearly visible. Abraham Darby III, the founder's grandson, enlarged it in the late 1770s to cast the iron components for the world's first iron bridge across the Severn at Ironbridge in 1779. The enlargement was done only on the front and left sides; the right could not be widened without moving the waterwheel that drove the bellows. So the furnace mouth ended up off-centre - a small architectural quirk that documents how craft, expedience, and revolutionary engineering coexisted at the same hearth. The lintels above the furnace bear inscriptions: "Abraham Darby 1777" recording the enlargement, and an older date that may read 1638 or 1658 (the painted version says 1638 but an archive photograph showed 1658). The exact pre-Darby history is still being unpicked by the museum's archaeologists.

Through the 18th century the Coalbrookdale Company made the infrastructure of industrialisation. Cast-iron cooking pots and kettles for domestic kitchens. Pig iron for other foundries. From 1723, cylinders for Newcomen atmospheric engines - the steam engines that pumped out flooded coal mines and made deep mining possible. Bigger boring facilities in 1734 let them cast cylinders up to 60 inches across, then 70 by mid-century. The company installed its own Newcomen engine in 1743 to recycle waterwheel water during summer droughts. In 1767 it produced the first cast-iron rails for railways. In 1802 it built a steam locomotive for Richard Trevithick - probably the first locomotive ever built for use, although it is unclear whether it actually ran (the death of a workman in an accident with the engine may have halted operations). Trevithick's first successful locomotive at Penydarren followed two years later. Cast-iron gates for London's Hyde Park were made here. So was the verandah at St John's in Monmouth, the Peacock Fountain that now stands in Christchurch, New Zealand, and the cylinders for Thomas Telford's revolutionary 1796 Longdon-on-Tern aqueduct.

In 1801 the French painter Philip James de Loutherbourg, fresh from the wars and looking for a subject for the age, came up the Severn Gorge and painted what he saw at the Madeley Wood furnaces. *Coalbrookdale by Night* shows the iron foundries against a low mountain horizon, lit not by the moon but by their own fires - orange and yellow glare from open furnaces, smoke catching the underside of clouds, men silhouetted as black sticks against the flames. It is one of the most famous images of the Industrial Revolution and possibly the first painting in European art to treat industry itself as sublime. The Coalbrookdale Company kept going long after this. It merged with Light Castings Limited and then Allied Ironfounders Limited in 1929, was absorbed by Glynwed which became Aga Foodservice (the famous Aga range cookers were made here for decades), and finally closed in November 2017 - 308 years after Abraham Darby lit his coke fire. The Ironbridge Gorge Museums now preserve the site, the Old Furnace, the Quaker burial ground, the Darby Houses, and the rather charmingly named Tea Kettle Row of workers' cottages. The whole gorge is a UNESCO World Heritage Site. Wood-smoke and birdsong fill the valley now where iron once ran molten down stone gutters.