1921 - Petroleum Resources of California, Bulletin 89
By 1921, the increasing demand for petroleum and its products, and the inability of production to keep pace with requirements, for several years, resulted in widespread prospecting throughout the world for possible new oil fields. In California, "wild-cat" wells were being drilled in many localities, some of them in places where even a cursory inspection of the geology would tell the futility of looking for oil. This report aimed to furnish information as to the unfavorable as well as the favorable areas of development of additional petroleum resources in California. The purpose of the report was to briefly take stock of the oil resources of the state and in particular to determine, if possible, the opportunity that existed for extending the productive area into districts that had previously been regarded as unfavorable.