Smithfield Street Bridge
Even in the “City of Bridges,” the Smithfield Street Bridge is in a class of its own. Spanning the Monongahela River and connecting downtown Pittsburgh with Station Square, what makes the bridge unique is its longevity and design. The double lenticular truss bridge was completed in 1883 and was designed by the Austrian born Gustav Lindenthal who also designed New York City’s Hell Gate Bridge. It is Pittsburgh’s oldest river bridge, attained National Historic Civic Engineering Landmark status in 1976, was designated a National Historic Landmark the same year, and has been listed on the National Register of Historic Places since 1974.
Backstory and Context
Two pervious bridges once stood where the Smithfield Bridge now crosses the Mon. In 1818, Louis Wernwag built a wooden covered toll bridge that was completely destroyed by Pittsburgh’s Great Fire of 1845. The next year, John Roebling, prior to beginning designs for the Brooklyn Bridge, built a wire suspension bridge where the wooden toll bridge once stood. However, the ever-increasing size and frequency of the loads crossing over it, as well as the larger boats on the Mon passing under it made Roebling’s bridge obsolete and it was gradually torn down as the new bridge replaced it beginning in 1880.
The Monongahela Bridge Company then contracted with Lindenthal to design a new bridge and construction began in 1881 while traffic still crossed Roebling’s suspension bridge. Lindenthal designed a double lenticular truss bridge, so named because the top and bottom chords curve into each other which creates a profile similar to a convex lens or horizontal cat’s pupil. The design transfers the load from the bridge deck out to the ends of the trusses, which rest on solid pylons or piers, in this instance, the same piers used by Roebling. Lindenthal’s bridge was an additional 20 feet above the river and featured two cast-iron towers with wrought iron roofs at each end when it opened in 1883. Lindenthal designed three other bridges in the Pittsburgh area: the 30th Street or Herr’s Island Bridge, the 7th Street or Andy Warhol Bridge, and the Youghiogheny River Bridge at McKeesport.
In 1861 a second bridge was built across the Mon (the South 10th Street Bridge) and due to that fact, Lindenthal’s bridge was eventually referred to as the Smithfield Street Bridge. The bridge has gone through numerous alterations and renovations over the years. A third truss to widen the bridge was temporarily added in 1891 and then removed in 1911 as the span was gradually widened from its original 23 feet to 48 feet. The city purchased the bridge in 1895 which opened it to the public free from tolls. It underwent a major renovation in 1911 as two lanes were dedicated for street cars and two for vehicles. Its original portals were also removed to be replaced in 1915, and its original color scheme was replaced with a solid, greyish-silver tone which remained until 1995.
The bridge deck was replaced with lighter aluminum in 1933 and again in 1967 and street cars stopped using the bridge in 1985. By 1993, the weakening structure had a weight limit of only three tons and buses had to be re-routed. The bridge was closed in 1994 for about a year, when the street car lines were removed, most of its metal frame was either replaced or repaired, additional structural supports were added and its original three-color scheme was restored. These renovations increased its weight capacity from three to 23 tons. Today, the Smithfield Street Bridge is as popular to stroll across as it is to drive and remains a shining jewel among Pittsburgh bridges.
"Smithfield Street Bridge." Brookline Connection. Accessed April 12, 2017. http://www.brooklineconnection.com/history/Facts/Smithfield.html
Jackson, Donald. "National Register of Historic Places -- Nomination Form." United States Department of the Interior/National Parks Service. March, 1973. Accessed April 12, 2017. http://historicbridges.org/truss/smithfield/nomination.pdf
Van Trump, James. "Historic American engineering Record: Smithfield Street Bridge, Pittsburgh (PA-2)." pgh bridges. 1974. Accessed April 12, 2017. http://pghbridges.com/articles/PA2-01.htm