The mammoth and merciless storm made landfall near Atlantic City around 8 p.m., with maximum sustained winds of about 80 miles per hour, the National Hurricane Center said. That was shortly after the center had reclassified the storm as a post-tropical cyclone, a scientific renaming that had no bearing on the powerful winds, driving rains, and life-threatening storm surge expected to accompany its push onto land.

The storm had unexpectedly picked up speed as it roared over the Atlantic Ocean on a slate-gray day and went on to paralyze life for millions of people in more than a half-dozen states, with extensive evacuations that turned shorefront neighborhoods into ghost towns.

The wind-driven rain lashed sea walls and protective barriers in places like Atlantic City, where the Boardwalk was damaged as water forced its way inland. Foam was spitting, and the sand gave in to the waves along the beach at Sandy Hook, N.J., at the entrance to New York Harbor. Water was thigh-high on the streets in Sea Bright, N.J., a 3-mile sand-sliver of a town where the ocean joined the Shrewsbury River.

‘‘It’s the worst I’ve seen,’’ said David Arnold, watching the storm from his longtime home in Long Branch, N.J. ‘‘The ocean is in the road; there are trees down everywhere. I’ve never seen it this bad.’’

The police said a tree fell on a house in Queens shortly after 7 p.m., killing a 30-year-old man. In Manhattan a few hours earlier, a construction crane atop one of the tallest buildings in the city came loose and dangled 80 stories over West 57th Street, across the street from Carnegie Hall.

Soon power was going out and water was rushing in. Waves topped the sea wall in the financial district in Manhattan, sending cars floating downstream. West Street, along the western edge of lower Manhattan, looked like a river. The Brooklyn-Battery Tunnel, known officially as the Hugh L. Carey Tunnel in memory of a former governor, flooded hours after Governor Andrew M. Cuomo of New York ordered it closed to traffic, and officials say water also seeped into subway tunnels.

Hurricane-force winds extended up to 175 miles from the center of the storm; tropical-storm-force winds spread out 485 miles from the center. Forecasters said tropical-storm-force winds could stretch all the way north to Canada and all the way west to the Great Lakes. Snow was expected in some states.

Businesses and schools were closed; roads, bridges, and tunnels were closed; and more than 13,000 airline flights were canceled. Even the Erie Canal was shut down.

Subways were shut down from Boston to Washington, as were Amtrak and the commuter rail lines. About 1,000 flights were canceled at each of the three major airports in the New York City area. Philadelphia International Airport had 1,200 canceled flights, according to FlightAware, a data provider in Houston. And late Monday night, Mayor Michael R. Bloomberg said cabs had been instructed to get off New York City roads.

By early evening, the storm knocked out power to hundreds of thousands of homes, stores, and office buildings. Consolidated Edison said 68,700 customers had lost power — 21,800 in Westchester County, 18,500 on Staten Island and 18,200 in Queens. In New Jersey, the Public Service Electric and Gas Co. said the storm had knocked out power to 36,000 customers. In Connecticut, nearly 70,000 people had lost electricity, utility officials reported. Con Edison, fearing damage to its electrical equipment, shut down power preemptively in sections of lower Manhattan, and then, at 8:30 p.m., a failure, probably caused by flooding in substations, knocked out power to most of Manhattan below Midtown, about 250,000 customers. About 10 p.m., Bloomberg said that NYU Langone Medical Center’s backup power system was not working and that patients were being moved out.