Formed right before the completion of Hoover Dam in 1934, Lake Mead is the largest man-made reservoir in North America, 180 km long, a surface area of 640 km^2, and 35 km^3 of water when full. However the lake has not been at full capacity since 1983 after years of drought and excessive water use in the parched American Southwest. Most of Lake Mead and Lake Mojave are under federal protection of the National Park Service (excepting the dam itself), initially as the Boulder Dam National Recreation Area (later Lake Mead National Recreation Area) the first National Recreation Area created in the United States (1936). It is a popular tourist spot for houseboating and water recreation, though water levels have dropped worryingly low in this year (2014).
Lake Mead from the top of Hoover Dam. The four penstock towers are part of the water intake system, and two are on each side of the border. The Nevada side has a clock with the Pacific Time Zone, while the Arizona side has a clock with the Mountain Time Zone (to confuse things further however, Arizona does not recognize Daylight Savings Time, so much of the year the clocks in fact have the same time).
Hoover Dam, Lake Mead National Recreation Area, Boulder City, Nevada/Arizona