Golden Gate Bridge

An orange suspension bridge spanning the Golden Gate strait; the world's longest suspension span when it opened.

When it opened on 27 May 1937, it had the longest main span of any suspension bridge in the world, 1,280 metres between its two towers, and the towers were the tallest of any suspension bridge, rising 227 metres above the water. It is one of the most photographed bridges on Earth and a famous symbol of San Francisco.

How it was built

Many experts said a bridge here was impossible because of strong tides, deep water, fierce winds and thick fog. Chief engineer Joseph Strauss led the project, with important design work by Leon Moisseiff, Charles Ellis and the architect Irving Morrow. Construction began on 5 January 1933 and finished ahead of schedule and under budget. Strauss had safety nets hung under the workers, which saved 19 men; they called themselves the "Half Way to Hell Club". Sadly, 11 workers still died in falls.

The towers and cables

Two main cables pass over the tops of the towers and are anchored into giant concrete blocks at each end. Each cable is almost a metre thick and made of 27,572 separate steel wires. Laid end to end, all the wire in both cables would stretch about 130,000 km, more than three times around the Earth. Each tower holds roughly 600,000 rivets. In the middle the road can move up or down by several metres as weight and temperature change.

Why it's orange

The colour is called International Orange. The architect Irving Morrow chose it because it fits the hills and sea around it and helps the bridge stand out in fog. The US Navy had suggested black and yellow stripes so ships could see it. A team of painters works all year touching up the paint to protect the steel from salty, foggy air.

On the globe

The model shows the orange suspension bridge stretched across the strait at the mouth of San Francisco Bay. Look for its two tall towers and the curving main cables between them.