On March 23, 1989, the oil tanker Exxon Valdez departed from the Valdez oil terminal in Valdez, Alaska (on its 28th voyage), heading south through Prince William Sound, with a full load (52 million gallons) of oil. Captain Joseph Hazelwood radioed to the Coast Guard station that he would be changing course in order to avoid some growlers, small icebergs which had drifted into the sound from the Columbia Glacier. The captain received permission to move into the northbound lane. Before retiring to his cabin, Captain Hazelwood instructed his third mate Gregory Cousins to "start coming back into the lanes" once the ship was abeam Busby Island Light, some 2 minutes ahead.

Although Cousins did give the instructions to the helmsman, a relapsed alcoholic, to steer the vessel to the right, the vessel was not turning sharply enough and at 12:04 a.m. on March 24, the vessel hit Bligh Reef. It is not known whether Cousins gave the orders too late or the helmsman did not follow instructions properly.

The spilled oil affected 1,900 km of Alaskan coastline. Although Exxon's initial report of 10.8 million gallons (40,900 m³) of oil spilled has been widely accepted, other sources estimate the spill at 35 million gallons (110,000 m³)