It was on this day in 1977 that the Trans-Alaska Pipeline began to pump oil for the first time. It was the largest private construction project ever completed in United States history.

Oil companies had been drilling for oil in Alaska for years, without much luck. Then the company that would become Exxon decided to drill one more hole before giving up, and they struck what turned out to be the largest oil discovery in North America. The only problem was that the oil field was 800 miles away from the nearest harbor where oil tankers could pick up the oil and transport it to the rest of the world.

So the oil companies decided to build a pipeline to transport that oil across the state of Alaska, 48-inches in diameter, stretching 800 miles, zigzagging over three mountain ranges and crossing 34 major rivers, including the Yukon. Once it began pumping, about 1.9 million barrels of crude oil began flowing through the pipe every day, traveling at about 7 miles an hour to the port of Valdez.