The Causey Arch is near Stanley in County Durham. It is the oldest surviving single-arch railway bridge in the world, and a key element of the industrial development of England.
It was built in 1725–26 by stonemason Ralph Wood. The cost of £12,000 was paid by an association of coal-owners founded by, amongst others, George Bowes, a descendant of the present Queen’s mother, he was the owner of the Gibside Estate upon which the bridge is situated.
Two tracks crossed the Arch: one to take coal to the River Tyne, and the other for returning the empty wagons. Over 900 horse-drawn wagons crossed the arch each day using the Tanfield Railway. The present Tanfield Railway runs very near to the bridge and is a steam railway run by volunteers.
When the bridge was completed in 1726, it was the longest single-span bridge in the country with an arch span of 31 metres (102 ft).
After he designed the bridge, Ralph Wood was so concerned that his arch would collapse that he committed suicide, but the bridge still stands today.