Many reasons are offered for covering bridges such as providing shelter during inclement weather or so horses wouldn’t be afraid to cross the water. However, the true reason is much more practical – to protect the structure supporting the bridge. Without protection from the weather, the wooden timbers supporting the bridge would decay more rapidly and eventually collapse.
America’s first documented covered bridge, called the Permanent Bridge, was constructed over the Schuylkill River in Philadelphia, Pennsylvania and opened to traffic on January 1, 1805. Timothy Palmer, who had been building uncovered structures throughout New England built it.
The Permanent Bridge had three arch supported trusses, two of them were 150 foot-long and the other was 195 feet long. It was built at a cost of $300,000. Because of the high cost it was decided that the bridge would be covered to protect the city’s investment.
It was expected to last about 40 to 50 years. Expanded to accommodate a railroad in 1850, it remained in service until being destroyed by fire on November 20, 1875.
Although there are some covered bridges whose construction dates are not known, it is believed that the oldest one remaining is the Hyde Hall Bridge in Glimmerglass State Park near Cooperstown, in Otsego County, New York. The 53 foot-long Burr truss bridge, built in 1825, was originally part of the Hyde Hall Estate.
The bridge was added to the National Register of Historic Places on December 17, 1998. (There may be a fee to visit it in the summer months.)
Types Of Covered Bridges
The term “historic” generally refers to those structures supported by wooden or mostly wooden trusses and built during the time when the use of wood was the most
economical choice. That included most of the 19th century and, depending on the region, may have extended to as late as the 1950s. However, from the historic preservation standpoint, any structure over 50 years old is often referred to as “historic.”
The term “modern” generally refers to wooden structures using truss designs developed during the waning years of the 1900s and early 2000s. While some may be constructed with solid wooden timbers, many use engineered wood such as glulam (glued laminated timber) to provide better support for heavy truck loads. The Cannon Bridge in Wyoming County, New York, opened to traffic during the summer of 2022.
“Non-traditional” or “stringer” bridges are ones which were not constructed with a load-bearing truss and are instead supported by wood beams, steel beams or a concrete deck. Some also use these terms to refer to historic bridges that have had steel beams or a concrete deck added underneath rendering the trusses non-functional.
An example is the Bob Dunning Memorial Bridge, a 60’ long pedestrian bridge over Willett Brook in Pondicherry Park in Cumberland County, Maine. Friends of Bob Dunning, a preservationist, craftsman and an environmental advocate, built it in 2010.
Locations of Covered Bridges
At this time there are around 828 traditional covered bridges in the country (about 2/3 of them historic) while there are over 2,700 non-traditional bridges. While some prefer to focus their attention on the historic structures, others are also interested in the modern designs and others will also travel to visit the non-traditional structures.
The National Society for the Preservation of Covered Bridges’ 2021 World Guide to Covered Bridges lists 211 covered bridges in Pennsylvania, the most of any state, followed by Ohio with 144.
New York State has 24 historic covered bridges, and another 19 more modern covered bridges for a total of 43. Vermont has just over 100 covered bridges.
Delaware and Ulster County, NY, have five historic bridges each, followed by Washington County, with four. Parke County, Indiana has the most covered bridges of any county in the United State with 31.
Longest Covered Bridges
The longest existing covered bridge is the Hartland Bridge in Hartland, New Brunswick, Canada. Built in 1901, the seven-span, 1,282 foot-long Howe truss structure was covered in 1922.
The longest covered bridge in the United States is the Smolen-Gulf Bridge over the Ashtabula River in Ashtabula County, Ohio. The four-span Pratt truss bridge was built in 2008 and is 613 feet long.
With a 210 foot open span, the Old Blenheim Bridge in Schoharie County, NY, is one of the longest single-span covered bridges in the United States.
The longest historic American covered bridge depends on how the length is measured. The Cornish-Windsor Bridge over the Connecticut River between Cornish, New Hampshire and Windsor, Vermont and the Medora Bridge in Medora, Indiana can both claim this title.
The truss of the Cornish-Windsor Bridge is longer than Medora’s 449.5’ vs. 434’. The span (distance between the faces of the abutments) of the Medora Bridge is greater than Cornish-Windsor’s, 430.4’ vs. 422’. The Cornish-Windsor Bridge is one of three covered crossings of the Connecticut River connecting New Hampshire and Vermont, the only places where covered bridges span two states.
Double Barrel Covered Bridges
The term “double-barrel” refers to a bridge with an additional truss in the center separating two travel lanes. There are only six of these bridges, five historic and one modern, in the United States:
- Ramp Creek or Brown County State Park in Indiana, built in 1838 and moved in 1932;
- Blenheim in Schoharie County, NY, built in 2018;
- Roberts in Preble County, Ohio, built in 1829 and moved to its present location in 1991;
- Cambridge Village or Museum in Chittendon County, Vermont built in 1845 and moved to its present location at the Shelburne Museum in 1951;
- Pulp Mill or Paper Mill in Middlebury and Weybridge, Addison County, Vermont, completed in 1854; and
- Philippi in Barbour County, West Virginia.
Railroad Covered Bridges
There are presently seven fully-covered railroad bridges:
- Contoocook Railroad in Contoocook, New Hampshire built in 1889, the oldest of the remaining covered railroad bridges;
- Pier Railroad or Chandler Station built near Newport, New Hampshire in 1907;
- Wright Railroad built near Newport, New Hampshire in 1906;
- Sulphite Railroad in Franklin, New Hampshire was built in 1896 and is the only known deck covered bridge, the traffic crosses over the top of the structure;
- Clark or Pinsley Railroad in Lincoln, New Hampshire which was built in Barre, Vermont in 1904 and moved to Clark’s Trading Post in 1965;
- East Shoreham Railroad in Addison County, Vermont was built in 1897 and abandoned in 1951; and
- Fisher Railroad or Chubb was built in 1908 near Wolcott in Lamoille County, Vermont.
Pony Truss Bridges
Once quite common, examples of boxed pony truss bridges are rare now. The term refers to the short trusses which are fully covered with siding. Similar to full-height examples, the trusses providing the structural support for the bridge are covered to protect them from the weather.
An example is the Trout Brook Bridge in Alna, Maine which was originally built for the Boston & Maine Railroad near Gorham, New Hampshire in 1918. After being a victim of arson in May 2004, the charred remains were given to the National Society for the Preservation of Covered Bridges.
Using a grant from the National Park Service, the trusses were reconstructed by Barns and Bridges of New England and used for Howe truss research at Case Western
Reserve University in Cleveland, Ohio. Once testing was complete, they were returned to Gorham to serve as a public exhibit.
Unable to find a suitable location, an offer was accepted to rebuild it on the Wiscasset, Waterville and Farmington Railway in Alna, Maine where it now carries rail traffic again.
The 2021 World Guide to Covered Bridges lists six other pony truss bridges: one in Connecticut, three in New Hampshire and two in Pennsylvania.
This essay is provided courtesy of the The National Society for the Preservation of Covered Bridges, whose mission is to preserve covered bridges, gather and record the history of covered bridges, collect and preserve covered bridge pictures ephemera of historical interest concerning covered bridges. This essay was drawn with their permission from “An Introductory Guide To Covered Bridges.”
Illustrations, from above: “Permanent Bridge with Covering and Tollhouse Portals” by William Strickland, 1815 (The University of Memphis); Hyde Hall Bridge in Cooperstown, NY (Todd Clark Collection); Hartland Bridge in Hartland, New Brunswick, (Bill and Jenn Caswell photo); Roberts Double Barrel Covered Bridge (David Simmons photo); Pier Railroad Covered Bridge (photo by Scott Wagner); and a pony truss covered bridge at Trout Brook Bridge in Alna, Maine (photo by Doug Turner).
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