Wooden covered bridges using patented Smith trusses were widely built in the American Midwest during the 25 years following the US Civil War (1865-1890). The geometry and construction of these bridges has proven puzzling to modern observers. The author, engaged in designing repairs to a Smith truss bridge at Cataract, Indiana, examined scribe marks, remnants of painted numbers and similar evidence left by the builders. This showed that some geometric complexities were a result of simple patterns used during layout and construction of the bridge. This was confirmed by inspection of seven other Smith trusses in Indiana and Ohio. The evidence left by the builders also sheds light on the design and manufacture of these bridges, illustrating how their inventor attempted to bring wooden bridge construction, with its roots in medieval timber framing, into the industrial age. The author feels that conservators studying style and structure - the realms of the architect and the engineer - may lose sight of the more prosaic world of the craftsman and builder. The insight gained regarding Smith trusses demonstrates how consideration of original construction methods and constraints can improve our understanding of historic structures.
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