The Hoover Dam, once known as the Boulder Dam, is a concrete arch-gravity dam that provides hydroelectric power.
It's a concrete arch-gravity dam and was built in 1930. It has a height of 726.4 feet tall from the foundation all the way up to the roadway on the crest of the dam. It weighs more than 6,600,000 tons, and is comprised of three and one-quarter million cubic yards of concrete. It can hold Five million cubic acres of water. It was named after President Hoover and built during the Depression. For a few decades, it was the largest and most important dam in the world.
After narrowly escaping the Junkyard of the Gods, Percy Jackson, Zoë Nightshade, Grover Underwood, and Thalia Grace travel by canoes to the Hoover Dam with the help of some water nymphs. Seeing Bessie the Ophiotaurus, Percy tells it that it shouldn't follow him and it could be in danger. With everyone tired, they decide to go to the dam snack bar, and make some dam jokes that Zoë doesn't understand. When the skeletons arrive, Percy is forced to hide in an elevator heading into the dam, where he encounters Athena, dressed as a tour guide, and Rachel Elizabeth Dare, a clear sighted mortal. Percy is surprised by Rachel and swings his sword at her, but it just phases through her because she is a mortal. She tells him to hide in the restroom as she leads the skeletons in the wrong direction. The group escapes using the two Angel Statues, who were sacred to Zeus. Thalia asks her father for help, the two statues wake up, and they fly away.
- It was said to be one of Annabeth's favorite pieces of architecture (evident as Percy, Grover, and Thalia spouted random facts that they subconsciously remembered, as Annabeth used to repeatedly go on about it).
- The name is the subject of some jokes by the characters; the word "dam" is pronounced the same way as a vulgar word, "damn" (the dam snack bar, a dam t-shirt, etc.), and the characters, who are tired and emotionally strung after the death of Bianca di Angelo, use the word to cheer themselves up. Zoë Nightshade does not understand the joke, even though she started it.
- In fact, the chapter in which the Hoover Dam first appears is fittingly called, "I Have a Dam Problem," in reference to the joke.
- The joke is later referenced in The Mark of Athena, in which Percy describes Piper's comparison of the open Doors of Death to a dam as "a dam hole." When asked about it, Percy simply brushes it off as an inside joke.