Covered Bridges in Pennsylvania

ASTM International has developed and published 12,000 standards devoted to the testing and classification of materials used in manufacturing and production to assure that those materials are of the utmost quality. ASTM is headquartered in West Conshohocken, Pennsylvania, in the same state where the most wooden covered bridges in the United States still reside.


Covered Bridge Truss
Covered Bridge Interior


Covered bridges are the product of Nineteenth Century standardization, when wood was the material of choice for such a structure. They are characterized by their truss design, which varies depending on the type of stream that the bridge crosses and the desired complexities during construction. Timothy Palmer constructed the original covered bridge over the Schuylkill River in Philadelphia in 1805. Interestingly, this wasn’t supposed to be covered when it was first installed, but due to a suggestion from adjacent neighbor of the bridge, Judge Richard Peters, the bridge was elegantly roofed, sided, and painted.

The rooftops of covered bridges were often designed to be aesthetically pleasing, but this was not their primary purpose. While the timber used in the construction of the bridges was sturdy and sound enough to support a reasonable load to cross a river or stream, it was still susceptible to rot from long-term exposure to weather. To prevent the wooden timber supports from decaying, roofs were used to block the sun, rain, and snow, significantly extending their lifespans.


Covered Bridge Pennsylvania
Covered Bridge in Lancaster County, Pennsylvania


With a roof and siding in place, a covered bridge ensured not only its longevity but also its status as an important symbol for travelers and the surrounding community. Covered bridges served the practical purposes of maintaining dry surfaces during storms, and they made it easy to transport cattle over streams, as the animals could not see the rushing water that often frightened them in open bridges. For the people on foot, covered bridges became a cool escape from the blistering summer temperatures or even a calm refuge during storms. The enclosed structures even became sites of intimacy and romance to some people due to their soft lighting, such as West Montrose Covered Bridge in Ontario, known by locals as the Kissing Bridge.

In this period, when the main mode of long-distance travel was the horse-and-buggy, covered bridges were certainly ideal, but they never would have been practical in the age of the automobile. However, the advent of the car didn’t kill the covered bridge, it was the growth of the steel industry. After the Civil War, the use of coal to smelt iron and steel made them much cheaper and easier to produce, and the metals were favored as the primary materials in bridges. Ironically, Pennsylvania, one of the biggest steel producers in the world, continued frequently making wooden covered bridges.

Of course, even in the state of Pennsylvania, where they were kept for their beauty, these covered bridges fell out of favor. The Lippincott Covered Bridge was built in 1943, long after others had been constructed in other states, but its construction can be attributed to the scarcity of steel during the war. At the peak of their construction, the state is estimated to have had about 1500 covered bridges, and the entire nation reportedly contained 14,000.


Zook's Mill Covered Bridge Lancaster County
Zook's Mill Covered Bridge over Cocalico Creek


American covered bridges in our time number only 900, 212 of which are found in Pennsylvania. For many, modern traffic is somewhat of a burden, and the bridges often become one-way passes that connect two-way streets. However, the loss of the majority of wooden covered bridges in the United States should not diminish their importance. The ones that remain have existed for over one century because of the care that was taken during and after their construction. Actions taken by the National Register of Historic Places have ensured that lasting bridges remain unharmed.

Today, in the same region as these lasting covered bridges and in close proximity to the original covered bridge, is ASTM International. ASTM was established in 1898, during the time when the local covered bridges were being installed in Pennsylvania. ASTM wood standards test lumber and timber materials so that they can be constructed into quality products. Under these guidelines and specifications, wood materials being produced now can be long lasting, and, like the covered bridges, give people in the future a glimpse into the past.
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