The Exxon Valdez runs into a reef in Prince William Sound, causing what would become the United States' second largest oil spill disaster.
According to MIT, several issues explain why the Valdez hit Bligh Reef. For one, the crew of the tanker, severely understaffed, did not know the U.S. Coast Guard had stopped escorting tankers beyond the reef. Valdez was supposed to have, but did not have, modern technology used to find icebergs and other obstacles. Exxon blamed the wreck on the Valdez's captain, Joseph Hazelwood, who was sleeping off a hangover during the accident. Other groups have since placed the blame on the third mate who was at the helm of the ship.
Numbers conflict on the exact amount of oil spilled. 11 million U.S. gallons was a long-estimated amount, but some later sources place the number of gallons spilled as high as 35 million. The oil covered 1,300 miles of coast line and 11,000 square miles of ocean.
The only larger oil disaster in U.S. history is the Deepwater Horizon oil spill in the Gulf of Mexico, estimated at 210 million gallons.