The Exxon Valez oil spill occurred in Prince William Sound, Alaska, United States, on March 24, 1989. It is considered one of the most devastating man-made environmental disasters ever to occur at sea. As significant as the Exxon Valdez spill was, it ranks well down on the list of the world's largest oil spills in terms of volume released. However, Prince William Sound's remote location (accessible only by helicopter and boat) made government and industry response efforts difficult and severely taxed existing plans for response. The region was a habitat for salmon, sea otters, seals, and seabirds. The vessel spilled 10.8 million U.S. gallons (40.9 million liters) of Prudhoe Bay crude oil into the sea, and the oil eventually covered 11,000 square miles (28,000 km²) of ocean.