On Aug. 14, 2003, the United States and Canada experienced the largest electrical power blackout in North American history. It was a massive power outage that affected parts of the northeastern U.S. and eastern Canada. Approximately 40 million people in eight U.S. states (about one-seventh of the population of the U.S.) and 10 million people in the Canadian province of Ontario (about one-third of the population of Canada) were impacted. The cost of financial losses related to the outage was estimated at $4 to $10 billion. The shutdown was the result of a monitoring and diagnostic systems failure coupled with communications problems between operations and support staffs, and a lack of systems understanding and planning by utility operators.