Petrolia (formerly, New Jerusalem and Petrolea) is an unincorporated community in Humboldt County, California. It is located 10 miles (16 km) southeast of Cape Mendocino, at an elevation of 121 feet (37 m). The ZIP Code is 95558. Petrolia has an estimated population of 300-500 people. It is located in the Mattole Valley, also known as the Lost Coast region for its proximity to the Lost Coast Wilderness area, one of the largest wilderness areas and the longest stretch of undeveloped coastline in the continental United States. The Lost Coast is named because of its position on the rocky, treacherous coastline and King Range of mountains that isolate this area from mainland California and continue to leave the area almost completely undeveloped.