The Beverly Hills Oil Field is a large and currently active oil field underneath part of the US cities of Beverly Hills, California, and portions of the adjacent city of Los Angeles. Discovered in 1900, and with a cumulative production of over 150 million barrels of oil, it ranks 39th by size among California's oil fields, and is unusual for being a large, continuously productive field in an entirely urban setting. All drilling, pumping, and processing operations for the 97[1] currently active wells are done from within four large "drilling islands", visible on Pico and Olympic boulevards as large windowless buildings, from which wells slant diagonally into different parts of the producing formations, directly underneath the multimillion-dollar residences and commercial structures of one of the wealthiest cities in the United States. Annual production from the field was 1.09 million barrels in 2006, 966,000 barrels in 2007, and 874,000 in 2008, and the field retains approximately 11 million barrels of oil in reserve, as estimated by the California Department of Conservation.[1][2] The largest operators as of 2009 were independent oil companies Plains Exploration & Production and BreitBurn Energy.[3]