The following are some of the cities that would be directly effected if the Hoover Dam were to break:
* Boulder City, Nevada: This city is located just below the downstream side of the Hoover Dam. If the dam were to fail, Boulder City would be completely flooded.
* Henderson, Nevada: This city is located about 15 miles downstream from the Hoover Dam. If the dam were to fail, Henderson would be flooded, but not completely.
* Las Vegas, Nevada: This city is located about 25 miles downstream from the Hoover Dam. Las Vegas would be seriously effected by a dam failure, but not completely destroyed. The flooding would likely reach the Las Vegas Strip, but it would not flood the entire city.
* North Las Vegas, Nevada: This city is located about 15 miles downstream from the Hoover Dam. If the dam were to fail, North Las Vegas would be flooded, but not completely.
* Laughlin, Nevada: This city is located about 75 miles downstream from the Hoover Dam. If the dam were to fail, Laughlin would be flooded, but not completely.
* Bullhead City, Arizona: This city is located about 10 miles downstream from the Hoover Dam. If the dam were to fail, Bullhead City would be completely flooded.
* Lake Havasu City, Arizona: This city is located about 100 miles downstream from the Hoover Dam. If the dam were to fail, Lake Havasu City would be flooded, but not completely.
* Yuma, Arizona: This city is located about 235 miles downstream from the Hoover Dam. If the dam were to fail, Yuma would be slightly effected by the flooding.
The cities mentioned above are just a few of those that would be effected by a Hoover Dam failure. The total number of people who would be displaced and the amount of damage that would be done would be impossible to estimate.