Historic Truss Bridges in Pennsylvania
A popular bridge type from the late 19th through the early 20th century, truss bridges are reminders of Pennsylvania’s technological history. These bridges often serve as community landmarks, due to their iconic structural features, but are aging and increasingly being lost due to the pressures of modern traffic demands. Not all of these bridges can be saved, but the Pennsylvania Department of Transportation (PennDOT) has developed a bridge marketing program for truss bridges eligible or listed on the National Register of Historic Places to encourage the relocation and reuse of historic bridges scheduled for replacement due to load and width limitations. Now you can own a piece of Pennsylvania history!
You can learn more about the Commonwealth’s bridge marketing program on our Historic Bridge Marketing page. If your organization or site is in the market for a bridge, please visit PennDOT’s Bridges for Sale page.
So What is a Historic Truss Bridge?
What is a truss bridge?
All bridges have 4 main characteristics: form, span, material, and travel surface in relation to the structure. A truss bridge is one form that a bridge can take and there are at least 30 different kinds of truss bridges, including the Warren, Pratt, and Howe designs among others.
Truss bridges can have any of the 3 span types including simple, continuous, or cantilever. They are often made of metal, specifically steel or iron, but can also be made of wood (such as covered bridges). The travel surface of a truss bridge may be called deck, pony, or through truss. A deck truss allows traffic to travel on top of the structure whereas a pony truss allows traffic to travel between two superstructures that do not connect at the top. Finally, a through truss is similar to pony truss, except the superstructures connect overhead.
What makes a truss bridge historic?
Many of the truss bridges offered for sale by PennDOT are either listed or are considered eligible for the National Register of Historic Places. Bridges with this distinction are locally, and even nationally, significant to U.S. history.
Metal truss bridges were very popular during their heyday from the late 19th through the early 20th centuries because they were inexpensive and easy to build. Engineers as well as other innovators came up with a large variety of patented designs which were then sold by agents across the nation.
Americans were granted more patents for metal truss bridges than any other country. These bridges represent an important piece of American engineering and architectural history. In Pennsylvania, they also represent the role of the famous iron and steel industries which manufactured many truss bridges. Now that the major iron and steel companies are gone, truss bridges remain as their legacy.
How can we preserve truss bridges?
Truss bridges can’t always carry modern traffic and may have to be sold and relocated through PennDOT’s Bridge Marketing Program. However, many truss bridges continue to serve drivers in Pennsylvania today, and some are even rehabilitated and repaired. For example, the Yellow Creek Bridge was rehabilitated in 2011 (see picture above).