Hoover Dam, which formed Lake Mead, is located in Black Canyon approximately 30 miles east of Las Vegas, NV in the Mojave Desert, Arizona-Nevada (Figure 1). At full pool, Lake Mead is the largest reservoir in the United States by volume and is second only to Lake Powell in surface area (Paulson and Baker 1983).
https://www.nps.gov/lake/learn/nature/overview-of-lake-mead.htm