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Iron Bridge
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Vital Statistics:
Location: Shropshire, England
Completion Date: 1779
Length: 100 feet
Type: Arch
Purpose: Roadway (original), Pedestrian (Today)
Materials: Cast iron
Longest Single Span: 100 feet
Engineer(s): Abraham Darby III, Thomas Farnolls Pritchard

The Severn Gorge in Shropshire, England, had all the resources necessary to become a thriving industrial area. The spectacular gorge was rich in coal, iron, and limestone, and the Severn River was the second busiest river in Europe. The only thing the thriving industrial community needed was a bridge to transport raw materials across the river to the industries in the valley. Shropshire had more iron factories within a two-mile radius than any other city in the world, so it seemed only logical to build the new bridge with iron.

Iron Bridge
Click photo
for larger image.

In 1773, architect Thomas Farnolls Pritchard proposed a single-arch bridge that would span the Severn Gorge. Arch bridges do not require supporting piers, so an arch across the Severn River would not block the passage of boats on the busy waterway. Unfortunately, Pritchard died in 1777, before the bridge was even built. Local businessmen commissioned Abraham Darby III, a local ironmaster, to complete the bridge.

Darby's bridge was the first in the world to be made entirely of cast iron. The bridge's arch spans 100 feet and has five arch ribs, each cast in two halves. All the major parts were put together in three months without a single accident or the least obstruction to the boats in the river. When it was finally complete, artists, writers, and engineers came from all over the world to marvel at the unique design. Today, the Iron Bridge is considered a British National Monument.

Here's how this bridge stacks up against some of the longest-spanning bridges in the world. (total length, in feet)
Chart showing the relative size of the longest bridges in the world
Iron Bridge 100'

Fast Facts:
  • Darby severely underestimated the cost to build the Iron Bridge. He remained in debt for the rest of his life.
  • In 1934, after years of repairs, the Iron Bridge was closed to vehicles and listed as an "Ancient Monument."
  • So many people gathered on the Iron Bridge in 1979 to celebrate its 200th birthday, pieces of the bridge actually broke off and dropped into the river. Today, no more than 200 people are allowed on the bridge at any time.