Wikipedia:
The Long Beach Oil Field is a large oil field underneath the cities of Long Beach and Signal Hill, California, in the United States. Discovered in 1921, the field was enormously productive in the 1920s, with hundreds of oil derricks covering Signal Hill and adjacent parts of Long Beach; largely due to the huge output of this field, the Los Angeles Basin produced one-fifth of the nation’s oil supply during the early 1920s. In 1923 alone the field produced over 68 million barrels of oil, and in barrels produced by surface area, the field was the world’s richest. During the early stages of the field’s development, unlike most oil fields, land was leased by the square inch instead of by the acre. The field is eighth-largest by cumulative production in California, and although now largely depleted, still officially retains around 5 million barrels of recoverable oil and has produced 963 million out of 3,600 million barrels of original oil in place. 294 wells remained in operation as of the beginning of 2008, and in 2008 the field reported production of over 1.5 million barrels of oil.
