Authorities warned that New York City and Long Island could get the worst of the storm surge: an 11-foot onslaught of seawater that could swamp lower Manhattan, flood the subways and cripple the underground network of electrical and communications lines that are vital to the nation's financial capital.
Because of Sandy's vast reach, with tropical storm-force winds extending almost 500 miles from its center, other major cities across the Northeast — Washington, Baltimore, Philadelphia and Boston — also prepared to for the worst.
"The days ahead are going to be very difficult," Maryland Gov. Martin O'Malley said. "There will be people who die and are killed in this storm."
Sheila Gladden evacuated her home in Philadelphia's flood-prone Eastwick neighborhood and headed to a hotel.
"I'm not going through this again," said Gladden, who had 5 1/2 feet of water in her home after Hurricane Floyd in 1999.
By early afternoon, the storm was 110 miles southeast of Atlantic City, its winds at 90 mph. It had speeded up to 28 mph and had begun the turn toward the coast that forecasters had feared.
As the storm closed in, it washed away an old section of the world-famous Atlantic City Boardwalk and left most of the city's emptied-out streets under water. All 12 casinos in the city were closed, and some 30,000 people were under orders to evacuate.
"When I think about how much water is already in the streets, and how much more is going to come with high tide tonight, this is going to be devastating. I think this is going to be a really bad situation tonight," said Bob McDevitt, president of the main Atlantic City casino workers union.
New Gov. Chris Christie, addressing those who were told to evacuate the state's barrier islands, said in his usual blunt way: "This is not a time to be a show-off. This is not a time to be stupid. This is the time to save yourself and your family."