On November 12 San Francisco will start a city-wide three-day celebration to inaugurate the opening of the San Francisco-Oakland Bay bridge to automobile traffic.

Commuters from Oakland, Berkeley and other points in the East Bay district will now make the actual crossing of the waters of San Francisco Bay by automobile in ten minutes, instead of the twenty minutes formerly spent on the ferry.

When Leland Stanford, one of the builders of the Central Pacific Railroad and founder of the university bearing his name, in 1867 proposed the building of such a bridge he was laughed down as a dreamer. He was told there were no adequate foundations in the bay for piers, and that it would be impossible to stretch a span from Yerba Buena Island to San Francisco.

In 1929 state engineers made a geological survey of the bottom of the bay. Borings revealed a high ridge of bedrock which could be used to provide a foundation at higher levels than the surrounding bedrock, and this led to the recommendation of the bridge route eventually selected.

The water along this route is from 50 to 105 feet deep, and bedrock lies from 100 to 200 feet below the mud at the bottom.

One of the many difficulties to be overcome was the financing of the bridge, but this was made possible by the availability of Federal Reconstruction Finance Corporation funds for the purchase of bonds of the California Toll Bridge Authority. It is estimated that the entire cost of the bridge—$77,200,000—will be recovered by 1954 out of revenue to be paid in the form of tolls collected from motorists and fares from interurban railway passengers.

The route for the bridge lay across Yerba Buena Island, a military base, and approval of the United States Army and Navy had to be obtained before anything could be done. However, permission was given for the boring of a tunnel 76 feet wide and 58 feet high through the highest part of the island.

The earth and rock removed from the anchorage sites in the tunnels were dumped into the middle of the bay, just north of Yerba Buena, to build up an area of 430 acres of shoal land. This has created an island on which the Golden Gate International Exposition of 1939 will be built. After the exposition the site will be used for a municipal airport and seaplane base, owned and operated by the city and county of San Francisco.

The San Francisco-Oakland Bay bridge is two types of bridge in combination. East of the island it consists of one main cantilever span 1400 feet long with two 510-foot anchor arms. East of this cantilever span are five truss spans, each 509 feet long, and 14 truss spans 291 feet long.

West of the island the structure consists of twin complete suspension bridges, each 4630 feet long joined end to end and having at their junction a common anchorage consisting of a massive concrete monolith topped by a steel shroud, rising 502 feet from the rock under the floor of the bay, with 282 feet above the water line.

Towers of the suspension bridge are from 474 to 519 feet high, and the piers range from 100 to 240.7 feet in depth. The deepest pier of the bridge is beneath the easterly end of the cantilever span and goes to a depth of 242 feet below the surface of the water.

Each individual tower, standing more than 700 feet high from the base of its pier on the floor of the bay to its tip, represents a construction job comparable to that of a 60-story skyscraper.

To commemorate the completion of the bridge a special silver half dollar has been minted, and 100,000 of these will be put into circulation on November 1.

Insurance on the bay bridge involves the largest amount ever written on a single unit risk in history. The bridge is insured for $36,000,000 against virtually all risks of loss or damage, with $8,000,000 additional covering use and occupancy.

Through the marine department the companies of Fireman’s Fund are carrying substantial lines.

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