Dig into the engineering of the Hoover Dam, a concrete arch-gravity dam on the Colorado River that supplies water to the US southwest. -- In the early 20th century, the US had expanded from coast to coast, but many cities in the southwest still lacked reliable water sources. The Colorado River's erratic flow and frequent floods made it unreliable for agriculture, and the region’s growing cities needed more energy. So the government decided to build a massive hydroelectric dam. Alex Gendler details the creation of the Hoover Dam. Lesson by Alex Gendler, directed by Jovan Rakic, Artrake Studio.