A covered bridge is an enclosed bridge consisting of two solid walls and a roof, with an opening on each end for \traffic. Covered bridges were historically constructed of wood, but in modern times, many have been reinforced with concrete and steel for preservation. Most commonly associated with early 19th century America, covered bridges around the country have become historic landmarks and tourist attractions. Europe and Asia are also known for their numerous covered bridges, both modern and historic.
The first covered bridge in North America appeared in 1804, and was built by bridge architect Thomas Palmer in Pennsylvania. However, covered bridges have been in use since medieval times in many European and Asian countries. Some notable surviving bridges around the world include the Japanese Covered bridge, built in Hoi An, Vietnam in 1595, and the Kappellbrucke Bridge built in Switzerland in 1333. The largest covered bridge known today is the Hartland Bridge in New Brunswick, Canada, which measures 1,282 feet (390.75 meters) long, and spans the Saint John River.
Covered bridges were initially covered due to their vulnerability to rot. A bridge made of wood may only last 10 or 15 years when exposed to the elements, but placing a roof over the structure would increase its lifespan by several decades. Wood is a plentiful building material in rural areas, and so covered bridges were built to cross rivers, streams and creeks in remote places. This explains the large number of surviving specimens in the Northeastern United States, as well as rural areas in other countries around the world.
Covered bridges in the United States also share a common color theme. Many were painted red, and historians believe this was helpful for coercing horses to enter. Farmers, traders and travelers equipped with horse-drawn carriages would have had a difficult time convincing their horses to cross over flowing water. The red paint is believed to have created the illusion of a barn, which convinced the horses to enter safely.
As time passed and construction methods improved, the covered bridge became a thing of the past. In the early 20th century, metal truss bridges began to take the place of the old wood construction, and soon the covered bridge was just a memory. There are around 800 covered bridges remaining in the United States today, and many of these still perform their original function. However, modern covered bridges are constructed only for convenience or style, rather than the original purpose of protecting the structure from weather.