Railroad bridges collapses

The development and expansion of the railroads in the nineteenth century required bridges, and timber provided the material of many of the early railroad bridges. It was a familiar material and one that was usually available near the construction site. However, timber bridges required maintenance to be sure they did not rot away, and they were susceptible to the very fire that the iron horses carried in their bellies. It was inevitable that iron was to become a natural replacement for wood in bridges, but the conversion took a good part of the nineteenth century, in large part because iron bridges seemed not only new but also unpredictable. They collapsed in numbers that are still debated today. 

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