Pakistanin Washington DC and nearby states after a blizzard blanketed the area with record snows.
Electricity was cut to at least 300,000 homes as the snow felled trees, and cut power lines. Emergency workers are struggling to restore power.
Washington got up to 2ft (61cm) of snow, one of the heaviest snowfalls in decades.
The storm disrupted transport from West Virginia to southern New Jersey.
A record 3ft (91cm) of snow fell on Maryland.
Washington DC, Virginia and Maryland have declared emergencies, allowing them to activate the National Guard to help cope with the wintry onslaught.
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Some 300,000 homes are without electricity in Maryland and neighbouring Virginia - the two states which bore the brunt of the storm.
Another 250,000 customers were hit by blackouts in Pennsylvania and New Jersey, the New York Times reported.
Pepco electric company said its workers were scrambling to restore power, but warned it could be a few days before everyone was back up.
"We have a lot of scattered outages and the road conditions are not really working with us," spokesman Andre Francis told AFP news agency.