Interesting facts about bridge. Bridges San Francisco Bay and connects with Oakland and East Bay. Work started 1913, date of completion 1937. Total length of bridge 4 1/4 miles. Longest span 2,310 feet. Highest tower 413 feet above water. Number of piers, 51. Steel used, 200,000 tons. Cables, 28 1/4 inches in diameter. Wires in each cable, 17,464. Total mileage of wires in cables, 70,000 miles. Concrete used, 1,000,000 cubit yards. Upper level provides six automobile lanes. Lower level three lanes for heavy traffic and two interurban lines. Total cost, about $75,000,000.