Translations:Adventist Youth Honors Answer Book/Arts and Crafts/Bridges/27/en
From Pathfinder Wiki
Because wood was so abundant in the United States, early truss bridges would typically use carefully fitted timbers for members taking compression and iron rods for tension members, usually constructed as a covered bridge to protect the structure. Truss bridges became a common type of bridge built from the 1870’s through the 1930’s. As metal slowly started to replace timber, wrought iron bridges in the U.S. started being built on a large scale in the 1870’s. Bowstring truss bridges were a common truss design seen during this time, with their arched top chords. As the 1880’s and 1890’s progressed, steel began to replace wrought iron as the preferred material.
