The pipeline was built between 1974 and 1977 after the 1973 oil crisis caused a sharp rise in oil prices in the United States. This rise made exploration of the Prudhoe Bay oil field economically feasible. Environmental, legal, and political debates followed the discovery of oil at Prudhoe Bay in 1968, and the pipeline was built only after the oil crisis provoked the passage of legislation designed to remove legal challenges to the project.