"Without covered bridges to span the rivers and provide access to vast swaths of the interior that had previously been difficult to access--America never would have developed the way she did. In America's Covered Bridges, authors Terry E. Miller and Ronald G. Knapp tell the fascinating story of these bridges, how they were built, the technological breakthroughs required to construct them, and above all the dedication and skill of their builders. Each of the bridges, whether still standing or long gone, has a story to tell about the nature of America at the time--not only about its transportational needs, but the availability of materials and the technological prowess of the people who built it. Central to the development of these bridges was the challenge of supporting a long spans with flat roadways. Early American bridge builders and carpenters developed revolutionary new methods of joining timbers into patterns consisting of triangles or continuous arches that resulted in structures rigid enough to span long distances. Called trusses, these systems were critical and had to be protected from the elements by a roof and siding. Few people today realize that bridges were covered to protect the trusses--not the people using the bridge! Unprotected, the trusses soon degraded and the bridge would collapse. North American covered bridges were marvels of engineering long before modern civil engineering was invented. Self-taught carpenters and builders discovered how to shape and join timbers into patterns in just the right ways to achieve a desired strength. Over time, wooden bridges eventually gave way to ones made of iron, steel, and concrete. Many covered bridges became obsolete and were replaced--others simply decayed and collapsed. Many more were swept away by raging torrents or ice floes, or by tornadoes, tropical storms, and hurricanes. A few were reduced to ashes by accidental fires, or torched by arsonists. Illustrated with some 550 historical and contemporary photos, paintings, and technical drawings of nearly 400 different covered bridges, the book offers five readable chapters on the history, design, and fate of America's covered bridges, plus related bridges in Canada."--Publisher's website.