New York City floods as Sandy slams into eastern U.S. | Anna Louie Sussman and Michael Erman

The skyline of lower Manhattan sits in darkness after a preventive power outage in New York October 29, 2012. Hurricane Sandy could be the biggest storm to hit the United States mainland when it comes ashore on Monday night, bringing strong winds and dangerous flooding to the East Coast from the mid-Atlantic states to New England, forecasters said on Sunday. Credit: Reuters/Keith Bedford

Oct. 30, 2012 -- NEW YORK (Reuters) - Millions of people in the eastern United States awoke Tuesday to flooded homes, fallen trees and widespread power outages caused by the giant storm Sandy, which swamped New York City's subway system and submerged streets in Manhattan's financial district.

At least 15 people were reported killed in the United States by Sandy, one of the biggest storms to ever hit the country, which dropped just below hurricane status before making landfall on Monday night in New Jersey.

More than 1 million people in a dozen states were under orders to evacuate as the massive system plowed westward.

One disaster forecasting company predicted economic losses could ultimately reach $20 billion, only half insured.

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