[citation needed] It is located in the Mattole Valley, part of the Lost Coast region, one of the largest wilderness areas and the longest stretch of undeveloped coastline in the continental United States.

"[9] The 35 miles (56 km) of steep roadways beneath the King Range mountains include towering Douglas firs, a few coastal redwoods around the upper reaches of the Mattole River, rocky shorelines, and black sand beaches, as well as a variety of California wildlife, including black bears, black-tailed deer, river otter, steelhead trout, California quail, bobcat and porcupine, reptiles such as rattlesnakes, western fence lizards and alligator lizards, various amphibians and bald eagles.

"[9][10] Petrolia is 5 miles (8.0 km) from the Pacific Ocean at the north end of the 25-mile (40 km) section of beach protected by the King Range National Conservation Area and Sinkyone Wilderness State Park; the Punta Gorda Light location is about 3 miles down the coast from Mattole Beach parking.

[12] Petrolia is located near the Mendocino triple junction, where three geologic fault lines meet, and experiences frequent earthquake activity.

The lack of any significant damage or land deformation was attributed to the shallow strike-slip fault movement in deep (3000m) water.

The South Cape Mendocino State Marine Reserve and Sugarloaf Rock are immediately offshore and are closed to public access.

[21][22] At the time of first contact with White settlers the area was inhabited by the Mattole, a Pacific Coast Athapaskan people,[23] who had arrived from today's Canada several hundred years earlier.

[2] The oil lay in small, fractured underground pools and ultimately, attempts to extract it dried up; the site is now registered as California Historical Landmark #543.

A few miles outside town at the former Walker ranch is a 400 by 20 feet (121.9 by 6.1 m) underground steel and concrete vault, built by the Scientology organization called Church of Spiritual Technology to hold "the wisdom of the ages.

[39] A number of writers and artists have made their home in Petrolia, including Alexander Cockburn, a left-wing journalist and founder of CounterPunch, Dale Maharidge, a journalist and winner of the Pulitzer Prize, Freeman House, an environmental author, Peter Hannaford, an author and political public relations specialist, Jim Danisch, a potter and sculptor, Jenny Scheinman, renowned violinist, Lisa Jo Jones, renowned actor, and Matteo Giglioli, Italian-American political scientist and author.

The Mattole Valley Historical Society holds occasional public meetings in Petrolia and conducts community walking tours, slideshows and talks about the history of the area and its founders.

[47] A race called the "Rye and Tide" combines bicycling and running from downtown Petrolia along Lighthouse Road 7 miles (11 km) to the ocean.

[48] Besides the general store, the Sunday farmers' market and cafe at the Community Center, and a new food cart downtown, the closest amenities are located in Ferndale, approximately 33 miles (53 km), a trip of over an hour by car.

Because of its isolation, the Mattole Valley has cultivated a reputation for independence and self-sustenance, including a network of local resources—the maintenance of its own emergency help line (augmenting 9-1-1).