Covered bridges were once a staple of rural life in many parts of the United States, generally affording carriages and pedestrians a safe and easy way to cross a river. While there were plenty of variations on the structural design of covered bridges, they are all recognized today simply by their characteristic roofs, which aren’t found on modern bridges.
The reason for adding a roof was quite simple, really. Nineteenth-century wooden bridges didn’t have advanced weather-resistant coatings, so they could only last so long when they were subjected to the rigors of nature. Rain puddled up on the floorboards and saturated the wood, the structure would ache under the weight of snow, and wind rocked the joints loose; with each passing year, bridges would become more and more ragged. Under those circumstances, early builders would be lucky if they could get 20 years out of each bridge before it needed to be replaced (or collapsed, whichever came first).
The solution was to add a roof to the bridge, and it proved a rather ingenious way to increase the life-span of the structure. Rain ran off the sides of the bridge’s roof, preventing water from pooling on the floorboards. Snow could be kept off the interior of the bridge and melt-water would be guided away by the pitch of roof. The floorboards, in general, were shielded from direct exposure to the elements, which allowed them last longer and remain safer for travelers. By adding a cover to bridges, their lives could easily be extended by three- or four-fold over an exposed bridge.
Even so, most covered bridges began to lose their usefulness in the early 20th-century. The advent of the automobile and growing populations in rural areas (where covered bridges found their greatest usefulness) were prime contributors to their decline. Cars and trucks allowed an ever-increasing population to travel more and more frequently. Covered bridges, with their simple wooden structure, just couldn’t last long enough under the strain of traffic. Across the nation, as covered bridges either collapsed or became too ragged to safely hold travelers, they were largely removed and replaced with stronger, more durable metal bridges… almost all of which no longer required a roof.
There are still hundreds of covered bridges left in the United States, though these represent a small fraction of the thousands that once existed. Many are closed to the use of heavy modern vehicles, but can still be walked upon by pedestrians. In other cases, these antique bridges have been fitted with stronger metal under-pinnings so that they can withstand continued vehicle traffic to this day.
The photograph above was taken in Vermont, which has over 100 covered bridges and boasts the highest ratio of “covered bridges per square mile” in the United States. Pennsylvania holds the record for the greatest overall number of bridges, though, with over 200.