A little over 3.3 million vehicles crossed the Golden Gate Bridge on the first year of operation. Between 1937-1967 the annual crossing rate grew by 70%. As congestion mounted, several studies were undertaken to identify alternate means of travel between Martin County and San Francicsco. The Martin County Transit district considered taking over the existing Greyhound system as a commute service to San Francisco. At that time,Greyhound provided transit between Marin and San Francisco, but it was unprofitable. Before its completion in 1937, it was considered unbuildable because of foggy weather, 60-per-hour winds, and strong ocean currents sweeping through a deep rugged canyon below. At a cost of 35 million, the 1.2-mile bridge took more then four years to build and 11 men lost their lives during construction.
San Francisco's Golden Gate Bridge could fail with an earthquake magnitude of 7.0 or greater. A plan for retrofitting, which could cost more than $200 million, will make the structure strong enough to withstand a magnitude of 8.3 shake.