The Hoover Dam is a massive concrete structure built during the Great Depression, located on the border between Nevada and Arizona. Completed in 1936, it holds back the Colorado River and created Lake Mead, the largest reservoir in the U.S. by volume. At 726 feet tall and 1,244 feet long, the dam is an engineering marvel — built to provide hydroelectric power, water storage, and flood control for the Southwest. It also supplies power to parts of Nevada, Arizona, and California. Today, it’s a popular tourist destination with incredible views, guided tours, and a chance to walk across the dam and stand in two states at once. The Art Deco design and sheer size make it both a historical and architectural icon.