The storm is being blamed for at least 74 deaths in the U.S., and property damage soared to $20 billion, making Sandy among the nation's costliest natural disasters.
President Barack Obama arrived in New Jersey on Wednesday, greeted by New Jersey Gov. Chris Christie. The two men surveyed the damage together on a helicopter tour.
"We are here for you, and we will not forget, we will follow up to make sure you get all the help you need until you've rebuilt," Mr. Obama said.
New Jersey was the hardest hit by the storm. Atlantic City was directly in the storm's path on Monday night, and part of the historic boardwalk washed away. Just in the city of Hoboken, officials estimate at least 20,000 people are stranded. National Guard troops spent the day helping the trapped and worn out residents.
"I can tell you that I have never seen devastation like this in my life, not here in New Jersey. You see sites like the Seaside Heights boardwalk, where the program 'The Jersey Shore' is filmed, the boardwalk is gone. It is gone," Christie said.
The president doled out hugs, handshakes and promises of military help to the people of New Jersey, while receiving praise from the Republican governor -- and one of Mitt Romney's top surrogates.
"I cannot thank the president enough for his personal concern and compassion for our state and for the people of our state," Christie said.
Several natural gas fires broke out in Mantaloking, N.J. Wednesday, but flooding is preventing crews from getting to the scene. Massive flooding wiped out a bridge on one side and there's flooding on the other. It's not clear what was burning or how the fires started.
Christie signed an executive order postponing Halloween trick-or-treating until Monday due to floodwaters, downed power lines, power outages and fallen trees.
"I've taken this action to minimize additional risks to lives and the public safety as we begin the process of rebuilding and recovering from Hurricane Sandy," Christie said.
Outages in the state's two largest cities, Newark and Jersey City, led to fender-benders at intersections where police were not directing traffic.
In New York, morning rush-hour traffic appeared thicker than on an ordinary day as people started to return to work without functioning subways. Cars were bumper to bumper on several major highways.
As emergency crews work around the clock to pump flood water out, lower Manhattan is still an unbelievable mess. In many places, there's still no power, traffic is jammed, and there's going to be a lot to clean up.
"All the water from the storm came in here like a tidal wave and flooded this whole area," said Al Linear, who was part of a crew cleaning up the Financial District. "Every building in this area is flooded, every one of them."
The New York Stock Exchange was able to reopen, but only because of generator power. Mayor Michael Bloomberg rang the bell to reopen it after a rare two-day closure.
Rescuers searched for two brothers from Staten Island, ages 2 and 4, missing since Tuesday. They were separated from their mother when their car was submerged during the storm and swept into a nearby marsh.
In Queens, there were seven incidents of looting in the storm-ravaged neighborhoods. Residents said they've watched in horror, as mobs ransacked shuttered stores, leaving with anything they could carry. Police arrested 15 people. Officials said the looting was not widespread.
"People were coming out with all kinds of stuff, everything. Whatever you can think of - from juices, sodas, waters, cigarettes, TVs. Anything you could think of, they were getting it," said George Watts of Coney Island.
At the height of the disaster, more than 8 million homes and businesses on the East Coast were without power. Authorities said the outages could stretch into next week. In lower Manhattan, power slowly began to come back on Wednesday, but more than 6 million customers remain without power across five states.
New Jersey and New York may have taken the brunt of Sandy's wrath, but the storm didn't quit there. In nearby Connecticut, homes along the Long Island Sound took a beating. A little further north in Rhode Island, beachfront homes either washed away or were in ruins.
From Maryland to West Virginia, mountain communities in eight states got up to two feet of snow. And from Cleveland to across the border in Toronto, Canada, full-grown downed trees are everywhere.
But there is a bit of good news for passengers hoping to travel in and out of the Northeast. John F. Kennedy International Airport in New York and Newark International Airport in New Jersey re-opened with limited service Wednesday morning. More than 18,000 flights were canceled as a result of Superstorm Sandy.
You can help victims of the storm by sending relief checks for the American Red Cross to ABC7. Checks can be made out to: American Red Cross, with Sandy Relief in the memo line. Send checks to:
Superstorm Sandy Relief
P.O. Box 5967
Glendale, CA 91221
The Associated Press contributed to this report.