1. St. Francis Dam, 1928
Self-taught engineer William Mulholland built this LA dam on a defective foundation and ignored the geology of the surrounding canyon. He also dismissed cracks that formed as soon as the reservoir behind it was filled. Five days later, it ruptured, killing 450 people and destroying entire towns (along with Mulholland’s career).
The other nine mistakes that are mentioned are also pretty horrific. Interesting that the guy was self-taught. These days an engineer that made that kind of mistake would likely be someone that plagiarized all his/her assignments and cheated on their exams. via Slash Dot, where a lot of other engineering disasters are mentioned in the comments.