Before we went I did a bit of research about the structures of covered bridges. In our area there were basically three truss designs. (Don't I sound just like an engineer?) There were the simple triangular Kingpost Truss bridges, which are the oldest in truss design and usually only cover short road spans of about 20 to 30 feet.
Next in the design chronology of covered bridges were the Queenpost Truss bridges. These incorporate an additional rectangular panel in the center. Typically this type of bridge spans longer distances, up to 75 feet.
And last, we find the Burr truss bridges, named for one of the earliest and most well known bridge builders in our country, Theodore Burr. His design became one of the more frequently used systems in bridge building. In these bridges you will see two long arches typically sandwiching a multiple Kingpost structure. There are more bridges in Pennsylvania using the Burr truss design than all other truss designs combined. You can compare the differences of the three types in this chart, however some bridges are a combination of design types:
On our drive we saw several of each kind of covered bridge. The 42 foot long Little Buffalo Covered Bridge was built about 1850. I had to get "lost" on the grounds of the Lewisburg Maximum Security Federal prison in order to find this one.
|You can clearly see the Kingpost (vertical beam) and its two diagonals.|
This 41 foot long Queen truss bridge, the Lawrence L. Knoebel Bridge, was built at another location in 1875, then dismantled and reconstructed at its present site in the Knoebel's Grove Amusement Park, Elysburg, Pennsylvania. You can easily see the extra rectangular panel in the design.
Built in 1830, Rishel Bridge is a 121 foot Burr truss bridge. Some experts consider this to be the oldest remaining original covered bridge in Pennsylvania. Look for the arch structure.
Built in 1880 at 63 feet, the Factory/Horsham Bridge has a modern king and queen truss structure.
All in all, it was a pleasant road trip, and I enjoyed trying to identify the type of structure of each new covered bridge we located. I learned from my reading that at one time, Pennsylvania had 1500 covered bridges.
My husband and I tried to imagine transportation back in those days. I'm sure traders were grateful to have a way to bring their wares across previously uncrossable waterways. I can imagine a young family moving to a new home waiting out a bad storm under the protective roof of a covered bridge. Perhaps a Sunday wagon ride to visit relatives was now possible, even in time for lunch.
I believe we can all look with pride at these wooden monuments that have weathered time and the elements. They are fun to find and look at. And please don't miss the graffiti!