Failure of the Teton Dam near Rexburg, Idaho on Saturday June 5, 1976. At 350 feet, this is the tallest dam that has ever failed.
The Teton Dam was an earthen dam in Idaho, United States, built by the Bureau of Reclamation, one of eight federal agencies authorized to construct dams. Located on the Teton River in the eastern part of the state, between Fremont and Madison counties, it suffered a catastrophic failure on June 5, 1976, as it was filling for the first time. (Source)
Even more impressive, you can watch it collapse:
And here’s the view from the other side:
There were 112 deaths associated with the construction of the dam. Included in that total was J. G. Tierney, a surveyor who drowned on December 20, 1922, while looking for an ideal spot for the dam. He is generally counted as the first man to die in the construction of Hoover Dam. His son, Patrick W. Tierney, was the last man to die working on the dam’s construction, 13 years to the day later.
*Here’s an actual aerial photo from 1950: