1937

Golden Gate Bridge

Joseph Strauss (1870–1938), Leon Moisseiff (1872–1943), Charles Alton Ellis (1876–1949)

At 4,200 feet (1,280 meters) long in its main span, the Golden Gate Bridge, opened in 1937, is still one of the top ten longest suspension bridges on earth today. Amazingly, engineers and hundreds of construction workers built this massive structure in just four years.

The original designer and chief engineer of the bridge was Joseph Strauss, assisted by Leo Moisseiff (who later designed the Tacoma Narrows Bridge). In collaboration with Moisseiff, senior engineer Charles Alton Ellis was the principal engineer for the project. The engineers judged that a suspension bridge with just two towers was optimal because the water in San Francisco Bay is so deep in the main channel, and many large ships enter San Francisco’s harbor. A multiple tower approach could not work on this site. Spanning the 4,200 feet between the two towers could not possibly be done with an arch, a truss, or cantilevered sections in any practical way.

The towers sit on massive concrete foundations poured on top of bedrock. The south tower is in the water, and 40-foot–thick (12 meters) fender walls made of steel-reinforced concrete surround its base. These walls prevent ships from crashing into the tower. The towers themselves are made of steel and rise to a height of 746 feet (227 meters) above the water.

The two main suspension cables are 3 feet (1 meter) in diameter. However, they are not solid steel. Instead, they were “spun” in place out of 27,000 lengths of steel wire. Two reasons why: first, it was the only practical way to do it, and second, the cables need to flex—in strong winds, the bridge moves up to 27 feet (8.2 meters) side to side. Suspender cables hang down to hold the deck for the road. Trusses support the deck between the suspender cables.

The last pieces of the puzzle are the two anchorages at the ends of the bridge. The towers are being pulled toward each other by the massive weight of the cables, deck, and roadway. To keep the towers standing, opposing cables pull them outward by attaching to anchorage blocks weighing 130 million pounds (60 million kg) each.

SEE ALSO Truss Bridge (1823), Tacoma Narrows Bridge (1940), Millau Viaduct (2004).

View from the southern tower of the Golden Gate Bridge.