National Geographic : 1956 Aug
183 Eight Miles of Steel Leap the Inland Sea Known as San Francisco Bay One of the seven wonders of American engineering, the San Francisco-Oakland Bay Bridge carries six lanes of automobile traffic on its upper deck, three lanes of trucks and buses and two train tracks below. An average of 92,000 vehicles cross it daily. Ships arrive and depart the landlocked harbor at the rate of one an hour. The city offers 18 miles of berthing, some deep enough for the largest vessels afia This freighter heads seaward.