On August 14, 2003, shortly after 2:00 pm. EDT, a high-voltage power line in northern Ohio brushed against some overgrown trees and shut down—a fault, as it’s known in the power industry. The line had softened
under the heat of the high current coursing through it. Normally, the problem would have tripped an alarm in the control room of FirstEnergy Corporation, an Ohio-based utility company, but the alarm system failed.
Over the next hour and a half, as system operators tried to understand what was happening, three other lines sagged into trees and switched off, forcing other power lines to shoulder an extra burden. Overtaxed, they cut out by 4:05 pm, tripping a cascade of failures throughout southeastern Canada and eight northeastern states. All told, 50 million people lost power for up to two days in the biggest blackout in North American history. The event contributed to at least eleven d eaths and cost an estimated $6 billion.