Also known as *the* blackout. https://en.wikipedia.org/wiki/Northeast_blackout_of_2003

Note that buggy software was a major contributing factor! The software was designed to, and would have, detected a deteriorating system an hour before anything broke, if not for a certain bug which caused the whole monitoring system to display stale data and then crash, including the redundant backup. This wasn't the only problem by far, but it was one layer of swiss cheese.