The golden Gate Bridge was built in 1933 to connect San Francisco to Marin County. There had been plans to build the bridge for decades, however it faced opposition from unions, the military and the railway company which ran the ferries. Before the bridge, the only way to cross the Golden Gate straight was by ferry. San Francisco was one of the last major US cities to rely on ferry links and the route was increasingly struggling to keep up with rising demand, caused by San Franciscos growing population and higher rates of car ownership. The bridge aimed to relieve that demand, help the San Francisco economy and, to a lesser extent, demonstrate America's engineering and industrial prowess to the world.
The real reason was to generate Revenue
Because it is the only way out of San Francisco on its north side, the bridge is part of both Interstate 101 and California State Route 1.
That time's government wanted to connect two valleys, and there was no other way to get through except boats which was not reliable for large amount of traveling, so they started to build up Gold Gate bridge.
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