As Superstorm Sandy churned slowly inland, millions along the US East Coast awoke Tuesday without power or mass transit, and huge swaths of New York City were unusually dark and abandoned. At least 20 people were killed in seven states, including 10 in New York. The storm that made landfall in New Jersey on Monday evening with 80 mph (130 kph) sustained winds cut power to more than 6 million homes and businesses from the Carolinas to Ohio and put the presidential campaign on hold one week before Election Day.

New York was among the hardest hit, with its financial heart closed for a second day and seawater cascading into the still-gaping construction pit at the World Trade Center. The storm caused the worst damage in the 108-year history of New York’s extensive subway system, according to Joseph Lhota, the chairman of the Metropolitan Transportation Authority.

“This will be one for the record books,” said John Miksad, senior vice president for electric operations at Consolidated Edison, which had more than 670,000 customers without power in and around New York City.

Trading at the New York Stock Exchange was canceled again Tuesday — the first time the exchange suspended operations for two consecutive days due to weather since a blizzard in 1888.

President Barack Obama declared a major disaster in New York and Long Island, making federal funding available to residents of the area.

New York City’s three major airports remained closed. Overall, more than 13,500 flights had been canceled for Monday and Tuesday, almost all related to the storm, according to the flight-tracking service FlightAware.

On the bright side, though, the New York Stock Exchange and the Nasdaq exchange announced they will reopen Wednesday after a two-day shutdown, the markets’ first closure since 9/11 attacks.