Cantilever bridge in the context of "Quebec Bridge"

A bridge is a structure that crosses an obstacle such as a river, lake, railroad, road, or ravine. Its primary function is to transport vehicles, trains, and pedestrians, but bridges may also accommodate pipelines, buildings, wildlife, and canals. Basic structures used in bridge design include arches, trusses, beams, cantilevers, suspension cables, and cable-stays. Bridges are configured in a variety of forms, such as viaducts, aqueducts, trestles, movable bridges, double-deckers, pontoons, and portable military bridges. They may also be categorized by their materials, which include wood, brick, stone, iron, steel, and concrete.

The history of bridges reflects the evolution of humankind's engineering technologies. The Romans and ancient Chinese built major bridges of stone and timber. During the Renaissance, advances in science and engineering led to wider bridge spans and more elegant designs. Concrete was perfected in the early 1800s, and proved to be superior to stone in many regards. With the Industrial Revolution came mass-produced steel, which enabled the creation of suspension and cable-stayed bridges that could span wide obstacles.

A cable-stayed bridge is a type of bridge that has one or more towers (or pylons), from which cables support the bridge deck. A distinctive feature are the cables or stays, which run directly from the tower to the deck, normally forming a fan-like pattern or a series of parallel lines. This is in contrast to the modern suspension bridge, where the cables supporting the deck are suspended vertically from the main cables, which run between the towers and are anchored at both ends of the bridge. The cable-stayed bridge is optimal for spans longer than cantilever bridges and shorter than suspension bridges. This is the range within which cantilever bridges would rapidly grow heavier, and suspension bridge cabling would be more costly.

Cable-stayed bridges found wide use in the late 19th century. Early examples, including the Brooklyn Bridge, often combined features from both the cable-stayed and suspension designs. Cable-stayed designs fell from favor in the early 20th century as larger gaps were bridged using pure suspension designs, and shorter ones using various systems built of reinforced concrete. It returned to prominence in the later 20th century when the combination of new materials, larger construction machinery, and the need to replace older bridges all lowered the relative price of these designs.

The Forth Bridge is a cantilever railway bridge across the Firth of Forth in the east of Scotland, 9 miles (14 kilometres) west of central Edinburgh. Completed in 1890, it is considered a symbol of Scotland (having been voted Scotland's greatest man-made wonder in 2016), and is a UNESCO World Heritage Site. It was designed by English engineers Sir John Fowler and Sir Benjamin Baker. It is sometimes referred to as the Forth Rail Bridge (to distinguish it from the adjacent Forth Road Bridge), although this is not its official name.

Construction of the bridge began in 1882 and it was opened on 4 March 1890 by the Duke of Rothesay, the future Edward VII. The bridge carries the Edinburgh–Aberdeen line across the Forth between the villages of South Queensferry and North Queensferry and has a total length of 2,467 metres (8,094 ft). When it opened it had the longest single cantilever bridge span in the world, until 1919 when the single 1,801 ft (549 m) span Quebec Bridge in Canada was completed. It continues to be the world's second-longest single cantilever span, with two spans of 1,709 feet (521 m).

The Carquinez Bridge is a pair of parallel bridges spanning the Carquinez Strait at the northeastern end of San Francisco Bay. They form the part of Interstate 80 between Crockett and Vallejo, California, United States.

The name Carquinez Bridge originally referred to a single cantilever bridge built in 1927, which was part of the direct route between San Francisco and Sacramento. A second parallel cantilever bridge was completed in 1958 to deal with the increased traffic.

Tower Bridge is a Grade I listed combined bascule, suspension, and, until 1960, cantilever bridge in London, built between 1886 and 1894, designed by Horace Jones and engineered by John Wolfe Barry with the help of Henry Marc Brunel. It crosses the River Thames close to the Tower of London and is one of five London bridges owned and maintained by the City Bridge Foundation, a charitable trust founded in 1282.

The bridge was constructed to connect the 39% of London's population that lived east of London Bridge, equivalent to the populations of "Manchester on the one side, and Liverpool on the other", while allowing shipping to access the Pool of London between the Tower of London and London Bridge. The bridge was opened by Edward, Prince of Wales, and Alexandra, Princess of Wales, on 30 June 1894.

This list of cantilever bridges ranks the world's cantilever bridges by the length of their main span. A cantilever bridge is a bridge built using cantilevers: structures that project horizontally into space, supported on only one end.