In 1968, the largest oil strike in U.S. was discovered underneath Prudhoe Bay. Construction of the Trans-Alaskan Pipeline began in 1975, and the first oil left Prudhoe Bay on June 20, 1977. The pipeline runs 789 miles from Prudhoe Bay in the north to the port of Valdez in the south. It carries an average 1.8 million barrels of oils a day. Valdez is the northern most ice-free harbor in the U.S. When the oil reaches the marine terminal at Valdez it is transferred to waiting oil tankers.

The pipeline was built by the Alyeska Pipeline Service Company which was made up of a group of seven oil companies. In areas where there was stable rock and soil, the pipeline was buried. In the unstable areas of permafrost, the pipeline remains above ground. It is insulated and supported by 78,000 supports, located 60 feet apart. The pipeline is built in a flexible zigzag pattern. There are more than 800 river and stream crossings, and the pipeline passes through three mountain rangers. It has been called one of man's greatest engineering feats. 

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In late March, 1989, an oil tanker spilled 260,000 to 750,000 barrels of crude oil into Prince William Sound. This has been considered one of the worst human-caused environmental disasters in history. It was the largest oil spill in U.S. history until the Deepwater Horizon spill in the Gulf of Mexico in 2010. While the Deepwater spill was horrific, due to Prince William Sound's remote geography that is accessible only by air and water, government and industry was much slower than the Gulf spill, consequently causing more damage. 

The Sound is a habitat for world-class salmon fishing, sea otters, seals and all kind of seabirds. These were all affected by the oil spill. The oil came from top of the pipeline in the Prudhoe Bay oil fields and when spilled, spread out over 1,300 (2,100 km) of coastline and 11,000 square miles (28,000 km²) of ocean.

Today, oil still remains. It is found in marine life that is consumed by other animals, as well as in the beaches of the Sound. Though there were overwhelming tragedies, some small measures of good have come from this spill: federal agencies such the National Park Service has made their response times quicker and most tanker hulls are doubled hulled so that if they do hit something, the hull will not rupture completely.