The Northeast blackout of 2003 was a massive power outage that affected parts of the Northeastern and Midwestern United States and Ontario, Canada, on August 14, 2003. The outage impacted about 55 million people. While power was restored to some areas within hours, full restoration took up to two days in places like New York City and Toronto. The cause was traced to a software bug at FirstEnergy, which prevented operators from redistributing load, leading to widespread failures in the electrical grid.