Four new oil fields to which 45,500,000 barrels of oil reserves have been assigned were discovered in California during 1939; extensions or revisions of existing fields added 257 million barrels of estimated ultimate production; total 302,500,000 barrels of new oil. The 1939 production in the state was 224,354,048 barrels. Estimated reserves were increased by 78,146,000 barrels of oil for a total of 3,178,500,000 barrels as of January 1, 1940.

Of more interest to petroleum geologists than merely 1939 statistical data might be a summary of geological endeavors and results in California during the past 20 years and a prophecy for the future. Geological employment and geophysical activity from 1920 to 1939 inclusive are summarized and are correlated with results: namely, new fields discovered, producing wells completed, reserves proved, dry holes drilled, et cetera. Progress of geological thought and changing exploration methods are traced and new developments made possible by deep drilling are outlined. It is concluded that more geological man-years than in the past will be necessary to discover and develop a unit quantity of California's new future oil and gas production.