We're scaling incredible heights on this episode of Travel Thru History. We visit a civil engineering wonder on the border of Arizona and Nevada - the Hoover Dam. This massive structure not only attracts about a million tourists each year to take in the overwhelming sight, it's also a functioning Hydroelectric Power Plant that works to create environmentally friendly power to Nevada, Arizona and parts of California. We'll take a peek inside the Arizona Powerhouse and learn what makes Hoover Dam such an important piece of American history. Then we'll speak with a professor who knows everything there is to know about America's favorite dam. Many men lost their lives during the construction of it during the Great Depression; all for the hope of developing an area of the country that was a bit sparsely populated at the time. Next, we'll give you an all access pass to a tunnel that was built right into the canyon wall in the 1930s. You'll learn the construction process and that the secret was in the labor force. So, I hope you're not afraid of heights. We're standing atop the most famous dam in the world, Hoover Dam on today's Travel Thru History.