Hurricane Sandy made landfall last night, bringing with it gale force winds and surging seas that breached the seawall when they reached Manhattan.
The storm threatens an 800-mile swathe of the US, from the Atlantic Ocean to the Great Lakes in the Mid-West.
New York and other cities closed their transit systems and schools, ordering mass evacuations from low-lying areas ahead of the storm surge.
By early yesterday morning, water was already topping the seawall in Manhattan's Battery Park City, one of the areas ordered to be evacuated by Mayor Michael Bloomberg.
He told 375,000 New Yorkers to evacuate and urged those who remained to leave immediately. "Conditions are deteriorating rapidly and the window for you getting out safely is closing," he said
President Obama who cancelled campaign events eight days before the US elections, echoed Mr Bloomberg's call to flee, saying: "When they tell you to evacuate, you need to evacuate. Do not delay. Don't pause. Don't question the instructions that are being given, because this is a serious storm and it could potentially have fatal consequences."
The president has signed nine emergency declarations covering New York, New Jersey, Massachusetts, Connecticut, Rhode Island, Delaware, Pennsylvania, Maryland and District of Columbia.
New York electric company Con Edison said it expected "record-size outages," with nearly 35,000 customers in lower Manhattan and Brooklyn likely to be hit.
The company is facing both falling trees knocking down power lines from above and flood waters swamping underground systems from below.
All US stock markets were closed yesterday and will remain shut today, with a plan to re-open on tomorrow if the storm passes.
The United Nations, Broadway theatres and New Jersey casinos were forced to close and more than two-thirds of East Coast oil refining capacity was in the process of shutting down.
More than 14,000 flights were cancelled, bridges and tunnels were closed, and national passenger rail operator Amtrak suspended nearly all service on the east coast.
The US Government told non-emergency workers in Washington, DC, to stay home.
Up and down the coast, worried residents in the hurricane's path packed stores, searching for generators, flashlights, batteries, food and other emergency supplies.
Johnny Lopez, an owner of Best Buy Wines and Liquors in Brooklyn, said he plans to stay open all day today.
"Crazy busy yesterday," he said. "It was like Thanksgiving."
Off North Carolina, the US Coast Guard rescued 14 of the 16 crew members who abandoned the replica tall ship HMS Bounty, using helicopters to lift them from life rafts. The Coast Guard continued to search for two missing crew members.
In New York, a crane atop a building on 57th Street in Manhattan partially collapsed, leaving it dangling high above the street. Police said they were closing the area to pedestrians.
Forecasters said Sandy was a rare, hybrid super storm – which some have dubbed "Frankenstorm"–- created by an Arctic jet stream wrapping itself around a tropical storm.
The combination of those two storms would have been bad enough, but meteorologists said there was a third storm at play – a system coming down from Canada. Moreover, the storm was coming ashore at high tide, which was pulled even higher by a full moon.
While Sandy does not pack the punch of Hurricane Katrina, which devastated New Orleans in 2005, it has been gathering strength. It killed 66 people in the Caribbean last week before pounding US coastal areas as it moved north.
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