A three-month investigation found that line failures and system errors combined to cause the power outage that hit much of the Northeast and Great Lakes portions of the United States, as well as parts of eastern Canada, on August 14, 2003. The blackout affected 50 million people, 40 million of them in the United States.

A task force headed by the U.S. Department of Energy and its Canadian counterparts delved into the sequence of events that caused the massive power failure. Investigators concluded that mistakes made by FirstEnergy Corporation of Akron, Ohio, had combined with heavy loads of power to stress the interstate electrical grid and cause its failure through a chain reaction. Just after 4:00 P.M. (EDT) on Friday, August 14, power was knocked out from Detroit to Toronto to New York City.

The widespread outage immediately affected water supplies, halted air transportation and subway systems, snarled ground transportation, and brought most distribution lines to a standstill—affecting the flow of food and other supplies. Though there were isolated reports of looting, crime was minimal, with New York City reporting a lower crime rate for the night of August 14 than usual. Eight deaths were related to the blackout.

Power began to be restored to some areas later that evening, but it was August 16 before all affected areas were back on line.

Two weeks later, on August 28, London experienced a blackout at the peak of evening rush hour. The outage paralyzed the British capital and left a half million commuters stranded. Power was restored within an hour. A utilities official said that the “freak event” was caused by two faults that happened in quick succession.

In late September 2003 there were also widespread power outages in Denmark, Sweden, and Italy. The blackout in Italy affected the entire nation (with the exception of Sardinia), or 57 million people. Because it happened overnight and on a weekend, the impact was minimal.

The blackouts drew attention to the need for system upgrades, improved maintenance, and more sophisticated alert systems to prevent such grid failures, which take both an economic and human toll.