|Ancestor||Truss bridge, others|
|Carries||Pedestrians, livestock, vehicles|
|Material||Typically wood beams with iron fittings and iron rods in tension|
|Falsework required||Determined by enclosed bridge structure, site conditions, and degree of prefabrication|
A covered bridge is a timber-truss bridge with a roof, decking, and siding, which in most covered bridges create an almost complete enclosure.  The purpose of the covering is to protect the wooden structural members from the weather. Uncovered wooden bridges typically have a lifespan of only 20 years because of the effects of rain and sun, but a covered bridge could last over 100 years.  In the United States, only about 1 in 10 survived the 20th century.  The relatively small number of surviving bridges is due to deliberate replacement, neglect, and the high cost of restoration. 
Typically, covered bridges are structures with longitudinal timber-trusses which form the bridge's backbone. Some were built as railway bridges, using very heavy timbers and doubled up lattice work. 
In Canada and the U.S., numerous timber covered bridges were built in the late 1700s to the late 1800s, reminiscent of earlier designs in Germany and Switzerland.   They tend to be in isolated places, making them vulnerable to vandalism and arson. 
The oldest surviving truss bridge in the world is the Kapellbrücke in Switzerland, first built in the 1300s. Modern-style timber truss bridges were pioneered in Switzerland in the mid-1700s.  Germany has 70 surviving historic wooden covered bridges. 
Most bridges were built to cross streams, and the majority had just a single span. Virtually all contained a single lane. A few two-lane bridges were built, having a third, central truss. 
Many different truss designs were used. One of the most popular designs was the Burr Truss, patented in 1817, which used an arch to bear the load, while the trusses kept the bridge rigid. Other designs included the King, Queen, Lattice, and Howe trusses.
Early trusses were designed with only a rough understanding of the engineering dynamics at work.  In 1847, American engineer Squire Whipple published the first correct analysis of the precise ways that a load is carried through the components of a truss,  which enabled him to design stronger bridges with fewer materials.
About 14,000 covered bridges have been built in the United States,  mostly in the years 1825 to 1875.  The first documented was the Permanent Bridge, completed in 1805 to span the Schuylkill River in Philadelphia.   However, most other early examples of covered bridges do not appear until the 1820s. Extant bridges from that decade include New York's Hyde Hall Bridge and Pennsylvania's Hassenplug Bridge, both built in 1825, and the Haverhill–Bath Covered Bridge and the Roberts Covered Bridge, in New Hampshire and Ohio respectively, both built in 1829. 
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.  The longest, historical covered bridges remaining in the United States are the Cornish–Windsor Bridge, spanning the Connecticut River between New Hampshire and Vermont, and Medora Bridge, spanning the East Fork of the White River in Indiana. Both lay some claim to the superlative depending upon how the length is measured. 
In the mid-1800s, the development of cheaper wrought iron and cast iron led to metal rather than timber trusses.  Metal structures did not need protection from the elements, so they no longer needed to be covered. The bridges also became obsolete because most were single-lane, had low width and height clearances, and could not support the heavy loads of modern traffic. 
As of 2004 [update] , there were about 750 left,  mostly in eastern and northern states. The 2021 World Guide to Covered Bridges lists 840 covered bridges, although it states that only 670 of those were standing when the 1959 edition was published. 
Between 1969 and 2015, the number of surviving covered bridges in Canada declined from about 400 to under 200. 
In 1900, Quebec had an estimated 1,000 covered bridges.  Relative to the rest of North America, Quebec was late in building covered bridges, with the busiest decade for construction being the 1930s.  Initially, the designs were varied, but around 1905, the design was standardised to the Town québécois, a variant on the lattice truss patented by Ithiel Town in 1820. The designer is unknown. About 500 of these were built in the first half of the 1900s.  They were often built by local settlers using local materials, according to standard plans.  The last agricultural colony was founded in 1948, and the last bridge was built by the Ministry of Colonisation in 1958 in Lebel-sur-Quévillon.  There are now 82 covered bridges in Quebec, Transports Québec including the Félix-Gabriel-Marchand Bridge, the province's longest covered bridge.  In Quebec covered bridges were sometimes known as pont rouges (red bridges) because of their typical colour.  : 11, 87
Like Quebec, New Brunswick continued to build covered bridges into the 1950s, peaking at about 400 covered bridges. These mostly used the Howe, Town, and Burr trusses. Today, there are 58 covered bridges in New Brunswick, including the world's longest, the Hartland Bridge. 
Ontario has just one remaining covered bridge, the West Montrose Covered Bridge.
Roofed, rather than covered bridges, have existed for centuries in southern Europe and Asia. In these cases, the cover is to protect the users of the bridge rather than the structure. Examples include:
In addition to being practical, covered bridges were popular venues for a variety of social activities  and are an enduring cultural icon;  for example:
A bridge is a structure built to span a physical obstacle without blocking the way underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually something that is otherwise difficult or impossible to cross. There are many different designs of bridges, each serving a particular purpose and applicable to different situations. Designs of bridges vary depending on factors such as the function of the bridge, the nature of the terrain where the bridge is constructed and anchored, and the material used to make it, and the funds available to build it.
The ancient Romans were the first civilization to build large, permanent bridges. Early Roman bridges used techniques introduced by Etruscan immigrants, but the Romans improved those skills, developing and enhancing methods such as arches and keystones. There were three major types of Roman bridge: wooden, pontoon, and stone. Early Roman bridges were wooden, but by the 2nd century stone was being used. Stone bridges used the arch as their basic structure, and most used concrete, the first use of this material in bridge-building.
An arch bridge is a bridge with abutments at each end shaped as a curved arch. Arch bridges work by transferring the weight of the bridge and its loads partially into a horizontal thrust restrained by the abutments at either side. A viaduct may be made from a series of arches, although other more economical structures are typically used today.
A cantilever bridge is a bridge built using structures that project horizontally into space, supported on only one end. For small footbridges, the cantilevers may be simple beams; however, large cantilever bridges designed to handle road or rail traffic use trusses built from structural steel, or box girders built from prestressed concrete.
A truss bridge is a bridge whose load-bearing superstructure is composed of a truss, a structure of connected elements, usually forming triangular units. The connected elements may be stressed from tension, compression, or sometimes both in response to dynamic loads. The basic types of truss bridges shown in this article have simple designs which could be easily analyzed by 19th and early 20th-century engineers. A truss bridge is economical to construct because it uses materials efficiently.
A footbridge is a bridge designed solely for pedestrians. While the primary meaning for a bridge is a structure which links "two points at a height above the ground", a footbridge can also be a lower structure, such as a boardwalk, that enables pedestrians to cross wet, fragile, or marshy land. Bridges range from stepping stones–possibly the earliest man-made structure to "bridge" water–to elaborate steel structures. Another early bridge would have been simply a fallen tree. In some cases a footbridge can be both functional and artistic.
A trestle bridge is a bridge composed of a number of short spans supported by closely spaced frames. A trestle is a rigid frame used as a support, historically a tripod used to support a stool or a pair of isosceles triangles joined at their apices by a plank or beam such as the support structure for a trestle table. Each supporting frame is a bent. A trestle differs from a viaduct in that viaducts have towers that support much longer spans and typically have a higher elevation.
The Kapellbrücke is a covered wooden footbridge spanning the river Reuss diagonally in the city of Lucerne in central Switzerland. Named after the nearby St. Peter's Chapel, the bridge is unique in containing a number of interior paintings dating back to the 17th century, although many of them were destroyed along with a larger part of the centuries-old bridge in a 1993 fire. Subsequently restored, the Kapellbrücke is the oldest wooden covered bridge in Europe, as well as the world's oldest surviving truss bridge. It serves as the city's symbol and as one of Switzerland's main tourist attractions.
The J. C. Van Horne Bridge is a Canadian steel through truss/steel deck truss bridge crossing the Restigouche River between Campbellton, New Brunswick, and Pointe-à-la-Croix, Quebec.
The Florenceville Bridge is a wooden covered bridge combined with a steel trusses which crosses the Saint John River at Florenceville, New Brunswick, Canada. Built in 1907, the 46.9 metre bridge has one wooden Howe truss span, four steel through trusses and one plate girder span. The bridge evolved from a five span uncovered Burr Truss bridge built in 1885. One Burr span was converted to a covered Howe truss and in 1907 the others were converted to steel thru trusses.
The Cornish–Windsor Covered Bridge is a 156-year-old, two-span, timber Town lattice-truss, interstate, covered bridge that crosses the Connecticut River between Cornish, New Hampshire, and Windsor, Vermont. Until 2008, when the Smolen–Gulf Bridge opened in Ohio, it had been the longest covered bridge in the United States.
The Sioux Narrows Bridge is a bridge on Highway 71 at Sioux Narrows, Ontario, which spans the Sioux Narrows strait between Regina Bay and Whitefish Bay on Lake of the Woods.
The Goodpasture Bridge spans the McKenzie River near the community of Vida in Lane County, Oregon, United States. It is the second longest covered bridge and one of the most photographed covered bridges in the state. The Goodpasture Bridge is listed on the National Register of Historic Places.
The Powerscourt Covered Bridge is a covered bridge that takes the First Concession Road across the Chateauguay River in Hinchinbrooke, Quebec. It is also known as the Percy Bridge.
A timber bridge or wooden bridge is a bridge that uses timber or wood as its principal structural material. One of the first forms of bridge, those of timber have been used since ancient times.
The Pont Grandchamp is a covered bridge that crosses the Rivière Bayonne at Sainte-Geneviève-de-Berthier, Quebec, Canada.
Chùa Cầu is a footbridge with a temple atop, located in Hoi An, Quang Nam Province, Vietnam. It is also referred to as "Cầu Nhật Bản", "Japanese Covered Bridge", or "Lai Viễn Kiều".
Ben Thuy Bridge 1 is a road bridge in the North Central Coast of Vietnam and is part of the National Route 1