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Nearly 14,000 authentic wooden covered bridges once existed in the United States. Today, less than 900 are still standing. Time and technology took its toll on the bridges until recent years when Federal grants became available for states to restore and rebuild many of the historic bridges that were on the verge of collapse.
Pennsylvania, Ohio, Indiana and Vermont have a combined total of over 550 authentic covered bridges with Pennsylvania leading the way with over 200. Many of the covered bridges still standing in the United States are over 150 years old.
Covered Bridge Manual, a publication of the Federal Highway Administration, April 2005, perhaps provides the best definition of a covered bridge. "A covered bridge is a timber structure supporting a deck surface that carries loads over an obstruction (e.g., a river). A covered bridge's structural components are protected from the elements by various coverings: walls, roofs and decks." The Covered Bridge Manual also defines what constitutes an authentic covered bridge: "The typical covered bridge uses heavy timber trusses to carry loads over an obstruction. The floor system spans between the longitudinal trusses, and distributes and carries the loads between those trusses. The bridge is completed by lateral bracing (elements that connect to each truss, or side, of the bridge), a wall system, and roof.
Covered Bridge Component Terminology can be confusing. Knowledge of some of its basic parts such as the abutment, brace, chord, portal, pier, etc., can help one to understand how a covered bridge is constructed.
Many believe that a bridge is covered to prevent animals from being spooked by the flowing waters below while entering or crossing the bridge. Another belief is that the animals would gladly cross the bridge thinking they were entering a barn. Even some believe the cover provides shelter for travelers in case of inclement weather. The only real reason to cover the bridges is to prevent deterioration of its wooden parts caused by weathering.
Finding correct information about covered bridges is a never-ending process. There will always be conflicting documentation regarding year built, builder, length of bridge, truss type and even the waterway it crosses. A perfect example would be Jericho Covered Bridge in Baltimore and Harford Counties. Its build date is frequently shown as 1858, when in fact it is 1865. Jericho's truss system is often stated as a Burr Arch (or Burr Arch with a Multiple Kingpost), omitting that it is also has a Queenpost. Some covered bridge websites suggest it is a Howe truss. The method to measure the length of the bridge varies widely. One process to determine the length is simply to measure the floor bed from end to end. Another is to measure from portal to portal. A third process to measure the length of the bridge is to measure underneath the bridge from the inside of one abutment to the other. This is referred to as the clear span. Ben and June Evans, authors of Pennsylvania's Covered Bridges: A Complete Guide and New England's Covered Bridges: A Complete Guide, determine the actual length using portal to portal. In the case of a sloping portal, their measurement is taken approximately four feet above the road surface. The Evans' books include a vast amount of information regarding Covered Bridge Terminology, Truss Types, methods for determining statistical information as well as providing readers with pictures, information and directions to all of the covered bridges in New England and Pennsylvania.
The National Society for the Preservation of Covered Bridges, Inc., publishes a book titled World Guide to Covered Bridges. The Guide assigns a number to all known authentic covered bridges using three sets of numerical digits. The first set assigns a number to each state alphabetically, so Alabama is 01, California 05, Maryland 20, etc. Recently, bridge enthusiasts have replaced these numbers with the official abbreviation of the state. AL, CA and MD would represent the above mentioned states. The second set of numerical digits represents the county, alphabetically, where the bridge resides. Blount County in Alabama would be 05. The third set of digits is a number assigned to a bridge in that county. Bridge 01-05-05 or AL-05-05 is Swann/Joy Covered Bridge, Blount County, Alabama. World Guide also includes the waterway the bridge crosses over, number of spans, length, year built, truss type and brief directions to the bridge.
There are various Societies for Covered Bridges that are dedicated to the promotion, preservation and restoration of these historic treasures. Besides the previously mentioned National Society, The Theodore Burr Covered Bridge Society of Pennsylvania, Inc., has a membership of over 500, of which many contribute much of their time and money to preservation efforts. Ohio, New York, Indiana, Vermont and Oregon all have very active Societies. Numerous covered bridge websites are found on the internet. One excellent site is Dale Travis Covered Bridge Website.
Please check back often to Maryland Covered Bridges. Updates are made as more information is discovered during ongoing research. Any comments, corrections, or suggestions are welcome.
Maryland Covered Bridges
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