The Hoover Dam is an American landmark and engineering feat. It stands 726 feet high and is about 660 feet thick at it's concrete base and about 45 feet thick at it's top. Millions travel every year to the Arizona-Nevada border to marvel at it's enormity.
Such a structure does not come into existence without a price though. The dam was built between 1931 and 1936. It took around 10,000 men to complete it, and over 100 of these men died during construction.
The first to die was J.G. Tierney, a US Bureau of Reclamation employee who fell to his death in the Colorado River on December 20, 1922. Exactly 13 years later on December 20, 1935, Tierney's son, Patrick, became the last person to die during construction when he fell from an intake tower.