Hoover Dam, located in southern Nevada approximately 30 minutes from downtown Las Vegas, is a testament to America's self-reliance and ingenuity.  Built during the Great Depression, it took less than five years, in a harsh and barren land, to build the largest dam of its time. Today, Hoover Dam is a "modern marvel" of our times. It is a National Historic Landmark (since 1985) and has been rated by the American Society of Civil Engineers as one of America's seven modern civil engineering wonders. A visit to Las Vegas is not complete without taking a tour of the dam.  Over one million tourists visit the dam each year.