Petrolia is a small unincorporated town located in Humboldt County, California with 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, comprising more than 67,500 acres (273 km²) of untouched wilderness. 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. Travel magazines have called this area "too lovely to be believed, perhaps too beautiful to last." It has been recognized as the top "Still Wild" place in California.The Mattole River flows through Petrolia and is one of only a handful of undammed rivers left in the country. Petrolia is five miles (8 km) from the Pacific Ocean, where the Lost Coast trailhead is located, the start of a 25-mile (40 km) section of beach protected by the King Range National Conservation Area and Sinkyone Wilderness State Park, and the Punta Gorda lighthouse. The Mattole River is home to a variety of California wildlife, including otters, Roosevelt elk, black-tailed deer, steelhead trout, more than 250 bird species, and an endangered salmon that was the subject of Totem Salmon, a book about the community's attempts over two decades to preserve the Mattole salmon. It is also one of the few remaining areas with virgin old-growth stands of Douglas fir.