Sandy killed at least six people in New Jersey, said Gov. Chris Christie, who had warned people in low-lying areas to evacuate. "We're lucky that more people didn't die as a result of folks ignoring those warnings," he told reporters.
A number of deaths were caused by the storm surge, downed electrical lines and cold weather.
The Lehigh County, Pennsylvania, coroner attributed the death of 86-year-old Theresa Schlitzer to hypothermia after she was found unconscious in her yard, CNN affiliate WHTM in Harrisburg reported.
Schlitzer died Tuesday after spending nearly 12 hours outside in the storm, the coroner told WHTM. Details about why Schlitzer was outside and how she became incapacitated were not immediately available.
Boats were washed onto front yards in the Staten Island neighborhood of Great Kills. Borough President James Molinaro said the water has mostly receded, but the damage is severe. Several people, including the two young boys, are missing.
In the same New York City borough, John Filipowicz, 51, and his 20-year-old son John were found dead after being buried under debris in the basement of their home after it was swamped by the storm surge, authorities told WCBS.
Commuters, homeowners and businesses, meanwhile, struggled with the loss of power and waterlogged or burned homes.
Many are still in need of basic supplies. President Barack Obama visited a shelter Wednesday in the hard-hit town of Brigantine, New Jersey, where he said he met a woman with an 8-month-old who had run out of diapers and formula.
"Those are the kinds of basic supplies and help that we can provide," he said.
Obama promised that the federal government "will not quit" until communities are cleaned up.
"We are not going to tolerate red tape, we are not going to tolerate bureaucracy," Obama said. "And I've instituted a 15-minute rule, essentially, on my team. You return everybody's phone calls in 15 minutes, whether it's the mayor's, the governor's, county officials'.
"If they need something, we figure out a way to say yes."
Christie asked for patience as crews worked to turn the power back on for more than 2 million people still in the dark. He toured Brigantine on Wednesday with Obama, who said utilities from across the country have pledged to send crews to New Jersey as soon as possible.
By early Thursday, the remnants of Superstorm Sandy headed north through Canada, with the last of its effects beginning to wind down along the Appalachian Mountains, according to the National Weather Service.
The storm brought 2 to 3 feet of snow to some areas in West Virginia and Maryland, leaving thousands without power. Several more inches of snow are possible in some areas before the storm ends this week, the weather service said.
A little less than 4.9 million customers across the eastern United States were still in the dark early Thursday, down from the nearly 8 million who lost power shortly after the storm hit.
CNN's Joe Sterling and Melissa Grey contributed to this report.
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