A covered bridge is a bridge, often single-lane, with enclosed sides and a roof. They have typically been wooden, although some newer ones are concrete or metal with glass sides. Mainly associated with the nineteenth century, covered bridges often serve as prominent local landmarks and have long attracted the attention of historic preservationists.
Early bridges were often made of wood, especially where it was a plentiful resource. Wooden bridges tended to deteriorate rapidly from exposure to the elements, having a useful lifespan of only nine years. Covering them protected their structural members, thus extending their life to 80 years or more.
Given the ready availability of steel, concrete, and other modern construction materials, most modern covered bridges are built either for the convenience of the user, rather than to protect the structure itself, or as a statement of style or design.