American Icons in Covered Bridges
I always wondered why bridges from the past were covered and upon reading stories and conversations with many people, the story that seems to stand out the most is that perhaps the horses felt at ease crossing an enclosed span instead of one that was opened. Another reason was perhaps that the bridges would last longer if the wooden timbers were protected from the elements. Whatever the reasons may have been, covered bridges have a long history in the North America.
Like any bridge that is built, covered ones were roadways that spanned rivers and streams. They were supported on each side by a wooden truss and a roof. The frame that supported this were built from very heavy timbers which were referred to as "chords". These chords were designed into two tall walls and cross timbers were placed at the top, bottom, ceiling, floor, and the foundation. The trusses were connected by the chords. Lastly, trunnels which are tree nails, were made of hardwood,which held the entire bridge together.
The very first covered bridge was built in over the Schuylkill River in Philadelphia, The builders on this project wanted to protect their investment so they added a roof and weather-boarding on the bridge. The bridge was ready for use in 1805.
A popular design for covered bridges was the "Burr-Truss", named appropriately for Theodore Burr who patented it in 1804. In 1817 Burr also patened the Burr arch bridge. Another bridge designer was Ithiel Town who designed the Town lattice design. His achievement was patented in 1835. Five years later in 1840, William Howe patented anothr new design that combined iron uprights with wooden supports.
The original wood products for covered bridges were pine, chestnut, poplar,oak, and walnut. The early covered bridges built were usually privately built and owned and operated as toll bridges. The charge for a person crossing was usually one cent and the same charge applied for the passage of a cow. The charge for a horse-drawn carriage was around four cents. Many bridges had posted signs that warned that a two dollar fine would be imposed if horses were not properly walked across a bridge. The reason behind this was because the vibration of galloping horses' hooves could possibly damage the wood structures and joints over a period of time. Basically the bridge owners wanted to protect thier investment and ensure safely for all those who crossed.
Farmers benefited greatly from covered bridges during the 1800s because it was easy for them to take their cattle, sheep, and hogs and even produce to various markets. Without a bridge, this would have been virtually impossible. One group that did not like the bridges were the ferry operators because it cost many of them their livelihood.
In the early 1900s, the bridges for one reason or another became very vulnerable to fires and floods, so they were being replaced by the overhead steel truss bridges.
There are many covered bridges around today but pale in comparison to the big ones that were built in the early 19th century. One of those was the 5,690 Columbia Wrightsville Bridge which spanned the Susquehanna River between Lancaster and York Counties located in Pennsylvania. Sadly to say, in 1832 floods and an ice jam destroyed the bridge.
Data from the American Society of covered Bridges states that there are about 1500 covered bridges around the world today. Of this number the United States has over 870. Canada has about 180. The state of Pennsylvania can proudly stake their claim by having about 291 covered bridges existing today.
These iconic covered and useful bridges of the past added beauty to the landscape of countrysides two centuries ago and still hold that same beauty today with much nostalgia to share and go around.