Golden Gate Bridge, one of the world's most recognizable landmarks, is the result of determination and complicated mathematics. It took four years to build and cost $27 million.

Scientists and mathematicians were consulted, to make sure that the bridge could withstand heavy vehicle traffic and heavy winds. Also, the area had suffered a massive earthquake as recently as 1906, and so extra attention was devoted to making the bridge earthquake-safe. When the city suffered another major quake, in 1989, the bridge survived intact.

Many unique features of the bridge and its construction are worth mentioning:

• The official color of the bridge is International Orange. This color was chosen mainly because of its visibility in fog, which is prevalent in the area.
• The bridge's suspension span is 4,200 feet in length.
• The bridge was named for the Golden Gate Strait, the entrance to the San Francisco Bay from the Pacific Ocean. The strait was named by John C. Fremont, one of California's main explorers, who thought that the strait reminded him of a harbor in Istanbul, Turkey, called the Golden Horn.
• A safety net was set up beneath the bridge, all the way along. As a result, fewer deaths were recorded than on other bridge-building projects. A total of 11 men died; the net saved 19.
• The bridge is the only road out of San Francisco to the north. Consequently, it is very busy at all times. Six lanes of traffic cross the bridge. Small, movable markers designate lanes. In the morning, when most people are coming south across the bridge into San Francisco, the six lanes are divided into four southbound and two northbound lanes. In the evening, it is the reverse.
• The bridge has walkways on both sides of the six lanes of traffic. The eastern walkway is used primarily by pedestrians, and the western walkway is used primarily by bicyclists. Both walkways are closed to pedestrians at night.
• Drivers going north across the bridge pay nothing. Southbound drivers pay a toll of $5. This one-way toll system was begun on October 19, 1968, making the Golden Gate Bridge the first major bridge in the world to do so. Other bridges soon followed this example.
• A group of 17 ironworkers and 38 painters maintain the safety and paint of the bridge. The paint is a special material that helps to protect the steel of the bridge from rust.
• Estimates for building this famous bridge in today's dollars routinely set a cost of $1.2 billion.
• Close to 2 billion vehicles have crossed the bridge.