Chimps nightime story

Hoover Dam (original name was Boulder Dam) took 5 years to build. It is one of the largest dams in the world at 726 ft. (221 m) high and 1,244 ft. (379 m) long. There are 4,360,000 cubic yards of concrete in the dam, powerplant, and appurtenant works, about 5 million barrels of cement. The hydroelectric capacity of Hoover Dam is 1,345 Mw.

When the dam was built, there were theories that the enormous concentration of concrete in one spot would throw the earth off its axis. If this happened, some of the smaller countries were planning to sue for reparations in the World Court.
About 20 years ago, the administrator of the dam decided he didn't like the bats that lived there, so he had them exterminated. Needless to say, it is now plagued by insects. Attempts are being made to bring the bats back.
Although Las Vegas is only a 45 minute drive away from the dam (and half the time is spent on slow roads), it only gets about 2% of the dam's power output. This is because, when the dam was built and power was being assigned, the city only had a population of 6,000, and the mayor saw no reason for the population to increase by any significant amount.
The dam was originally expected to have a service life of 1,500 years. Now that other dams upstream of the Hoover Dam keep silt from accumulating under the dam, the expected lifetime has doubled to 3,000 years.
Watching specials on The History Channel, you will hear that about 100 people died during work on the dam. The number is actually over 400, but because the government listed Carbon Monoxide poisoning and Black Lung as unrelated diseases, most of these deaths were not listed as occupation-related.
At the top of the Dam, there is a star map that gives the appearance of the sky at the time that the dam was completed, as well as a description of the earth's axial wobble, so that archaeologists of the distant future might be able to fix the time that the dam was built.
The Hoover Dam is the only US Federal Public Works project of its size that has (directly) paid for itself.