The Smithfield Street Bridge is America's oldest steel truss bridge and an International Engineering Landmark, as well as on the National Register as a Historic Landmark.
Gustav Lindenthal, the "Dean of Bridge Engineers," designed the bridge in 1881. Recognizing the importance of the span to Pittsburgh's urban landscape, Lindenthal selected the elegant lens-shaped or lenticular truss design for its graceful symmetry. The innovative use of structural steel-instead of iron-symbolized Pittsburgh's emerging new steel technology.
The existing bridge has seen many changes during a century of service. First built as a single-road span with Victorian portals at both ends, it was widened on the upstream side in 1891 and again in 1911 to accommodate two trolley tracks. Four years later the bridge was beautified with new portals and small sculptures of Pittsburgh industrial workers. To lighten the weight of the structure in 1934, new aluminum decking and railings were installed. This was the first structural use of aluminum in bridge construction.
The first "Monongahela Bridge" crossed the river at this site in 1818, but was washed away by a flood in 1832. Its replacement, another wooden covered bridge, was destroyed by the great Pittsburgh fire of 1845. The brilliant engineer John Roebling next built a flexible
wire-suspension bridge to carry the heavy traffic, until the current Smithfield Street Bridge replacement it. Over the early bridges crossed covered wagons heading west to the frontier, and countless wagons full of coal mined from Mt. Washington-coal needed to heat the homes and fire the furnaces of industrial Pittsburgh.
In 1994, this bridge was restored and painted with the original colors used in 1915. Today it symbolizes Pittsburgh's historic creativity in bridge design and steel construction.