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, which would have provided ample time to intervene. However, a race condition 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.

Also note the power companies have clear procedures to reboot the grid, known as a "black start[up]". And they test these procedures, though without taking down the grid.