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. Pennsylvania has the most covered bridges with a total of 213 and Ohio is second with 148 with the most in one county at Parke County, Indiana with 31.

About 14,000 covered bridges have been built in the United States, mostly in the years 1825 to 1875. The longest covered bridge ever built was constructed in 1814 in Lancaster County, Pennsylvania, and spanned over a mile in length, but was destroyed by ice and flooding in 1832. Early bridges were made of wood because when almost everything was made of wood because of its abundance. Working with wood, like any material, has its advantages and disadvantages. Timber is lighter than stone and cheaper than iron or steel, but still very strong. However, wood also deteriorates faster.

The earliest documented covered bridge was the 550' Permanent Bridge constructed over the Schuylkill River in Philadelphia by Timothy Palmer in 1805 and oldest documented American covered bridge is the Hyde Hall Bridge in Glimmerglass State Park near Cooperstown, New York. It was built in 1825. The covered bridge numbering system was developed in Ohio in the 1950's. The system was adopted for the NSPCB's World Guide to Covered Bridges in 1959. The first set of numbers represents the state/province in alphabetical order. Letters are used for bridges outside the United States and Canada. The second set of numbers represents the county in alphabetical order. The third set indicates the specific bridge within that county. A "#2" at the end of the number indicates that this is not the first covered bridge at this location.