At one time there were more than ten thousand covered bridges in the U.S., and today 54 of the remaining 750 are in New Hampshire. Covered bridges became the first type of historic structures specifically protected by state law here.
Why were covered bridges covered? According to the president of the Covered Bridge Society, “Our country was abundant in timber, so it was only natural to build bridges of wood. But, they found that after a few years, the bridges would start to rot, and repairs would have to be made. Rain and sun upon the truss quickly deteriorated the wood if left exposed. But American ingenuity provided a work-around: If you build walls and a roof over the bridge, it will be the walls and roof that rot, not the bridge. And, doing maintenance to the walls and roof is easy, compared with building a new bridge. This is the only reason we have covered bridges — to protect the wood that they are made with.”