The oil industry has provided trillions of gallons of affordable fuel and other petroleum products since the first commercial oil well was drilled in 1859. Since that first oil well started pumping, thousands of oil spills have occurred on land and at sea. Oil wells, pipelines, and oil tankers have all been sources of some major accidental leaks.
Here are what Wikipedia and Cleaner Seas together identify as the biggest oil spills in history. If intentional oil spills were considered, the Gulf War oil spill in 1991 would be the largest ever, and by a wide margin. The following list goes from largest to smallest based on the estimated amount of oil spilled. The environmental impact of a spill varies widely by location, type, the volume of oil, and other factors. The financial cost of each spill would likewise depend on a range of factors aside from the volume of oil spilled.
The Lakeview Gusher is the largest accidental oil spill in history, by a wide margin. This Kern, California spill dumped an estimated 378 million gallons of oil from March 1910 to September 1911. The owner, Lakeview Oil Company, had expected to extract natural gas and some oil, but pressure blew out the well and storage tanks designed to hold oil quickly overflowed. Given the amount of oil extracted from wells at sea or transported by oil tankers, it makes sense that many of the worst spills took place at sea.
The explosion and subsequent leak from a British Petroleum oil well in the Gulf of Mexico leaked between 172 million and 181 million gallons of oil from April through September 19, 2010 when the leak was apparently stopped. However, leaking may have continued into 2012. Along with killing or contaminating birds and fish, the oil contaminated at least 55 miles of Louisiana beaches. They found oil and dispersant chemicals as far away as central Florida, on the beaches of Tampa Bay.
An experimental well drilled off the coast of Mexico experienced a blowout and leaked oil into the Bay of Campeche. This spill released between 140 million and 148 million gallons of oil from June 1979 through March 1980. A blowout preventer that might have sealed the well near the sea floor failed. The leaking oil and natural gas exploded when they reached pump motors on the oil rig, making the leak even worse.
Atlantic Empress/Aegean Captain
On July 19, 1979, the Atlantic Empress collided with the Aegean Captain near Trinidad and Tobago. The collision damage and a couple of explosions lead to oil leaks that spilled 88 million gallons of oil into the Caribbean from each ship. In addition to the environmental damage caused, the collision and subsequent fires killed 26 crew members on the two ships. This remains the largest oil from a ship, by a wide margin. The famous Exxon Valdez spill dumped only a tiny fraction of the oil but caused vastly more environmental damage.
Fergana Valley, Uzbekistan
In 1992 a blowout at a well in the Mingbulak oil field in Uzbekistan resulted in the worst terrestrial oil spill ever recorded in Asia. The spill released 87.8 million gallons of oil before the flow of oil stopped on its own. Workers managed to contain some of the oil behind earthen dikes. However, most of it burned over the course of two months or soaked into the ground or was otherwise lost.
Kovla River Pipeline Leak, Russia
An oil pipeline near the Kovla River in Russia sprung a massive leak on August 6, 1983, which produced the third largest land oil spill in history. An estimated 84 million gallons of oil was dumped into the local ecosystem before it could be plugged. An emergency dike failed in cold weather that came soon after the spill. The oil contaminated a huge area of streams, bogs, and marshes.
Nowruz Oil Platform, Persian Gulf
In 1983, a pair of leaks spilled 80 million gallons of oil into the Gulf. This spill actually involves two oil wells in the same field that had uncontrolled leaks. In the first case, a tanker hit the oil platform and caused a leak. In the second case, in March of 1983, Iraqi attack helicopters hit another platform and caused a leak there. The first oil platform leak released about 50.8 million gallons of oil into the Arabian Gulf. Most of that loss of oil probably was due to the Iran-Iraq war, which delayed an effective response by the Iranian government. They did not assess the environmental impact at all. And several oil rig workers died while trying to plug the leak
ABT Summer, Angola
An oil tanker, the MV ABT Summer leaked 80 million gallons of oil into the South Atlantic. The spill happened about 810 miles off the coast of Angola when the supertanker ABT Sumer was damaged by an explosion. The ship burned for three days before sinking on June 1, 1999. This spill appears to have done relatively little environmental damage, though five of the crew died in the explosion.
Castillio de Beliver, South Africa
In August of 1983, the oil tanker Castillio de Beliver exploded 80 miles off of Table Rock, South Africa and began to burn. The wrecked tanker dumped an estimated 78.5 million gallons of oil into the South Atlantic. The oil created a slick 20 miles long. The massive fire and the huge oil slick did relatively little environmental damage because the slick moved out to sea rather than toward the coast. This spill injured and killed over 1,500 seabirds.
Amoco Cadiz, France
The oil tanker Amoco Cadiz ran aground three miles off the coast of Brittany in northern France on March 16, 1979. Due to severe weather, the ship broke apart. This means they could not pump out any of the crude or fuel oil. The wrecked ship spilled its cargo of 69.8 million gallons of light crude plus 4,000 tons of fuel oil. This is another ocean oil spill that seems to have done minimal environmental damage.