The purpose of the Golden Gate Bridge is to connect San Francisco to Marin County, Calif. Before the bridge opened in 1937, the only practical route between what is now Marin County and San Francisco was by ferry across San Francisco Bay. At the time, San Francisco was the largest U.S. city reached primarily by ferry.
Ferry service across the bay began around 1820. By the late 1920s, the Golden Gate Ferry Company was the world's largest ferry operation. San Francisco's growth rate before the bridge was built was lower than the national average because the city lacked an easy route to other cities around the bay.
Some experts believed that it was impossible to build a bridge across the bay, which is 6,700 feet wide. The bay had strong tides and currents, and water reached a depth of 372 feet at the center. Some experts felt that the frequent strong winds and fog prevented building and operating the bridge.
In 1933, construction of the Golden Gate Bridge began. Engineer Joseph Strauss designed the bridge. The bridge took four years, thousands of workers and $35 million to build. In May 1937, the bridge opened with 18,000 people walking across it. The following day, it was opened to traffic.