15 years ago the massive blackout swept the Northeast

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Fifteen years ago, a power outage swept across more than 50 million people in the United States and Canada. 

The Blackout of 2003 started the afternoon of August 14 and lasted for several days. Among the cities that lost all electrical power were New York City, Cleveland, Detroit, Toronto and Ottawa. 

The sudden shutdown of the power grid drove millions of people outdoors into stifling streets and trapped countless others in elevators and subways. Transmission lines and nuclear reactors all over the northeast failed within minutes of each other that day. 

New Yorkers scrambled down endless stairways from skyscrapers where elevators had stopped working. People in Manhattan hotels were even grabbing pillows and sleeping outside in the park in attempts to get any relief from the heat. 

The American Stock Exchange, New York Stock Exchange and Nasdaq never shut down, though, and reported minimal interruption after the close of trading. All had backup power generators. 

In Michigan, nearly all of DTE Energy's 2.1 million customers lost power. The Detroit-Windsor Tunnel was closed, and gambling machines at Detroit's Greektown Casino were silenced. Patrons filed into the afternoon heat carrying cups of tokens. 

Lights in some New York City neighborhoods were back on by the next morning, but the blackout lasted for multiple days in Michigan. FOX 2 was able to broadcast still with the use of generators. 

At first, authorities suspected the blackout was a terrorist attack but the FBI and Homeland Security eventually ruled out the possibility. At one point, Canadian authorities thought the cause was because lightning struck a power plant on the U.S. side of Niagara Falls. 

The problem was eventually traced back to overgrown tree limbs on some power lines in Ohio, which led to a domino effect of power plants failing due to outdated infrastructure. 

FOX Business reported the blackout cased up to $10 billion of damage to the economy.