The worst blizzard in seven years shut down much of the Northeast on Presidents Day with blinding, windblown snow that piled up as much as 4 feet deep and left more than a quarter of a million homes and businesses shivering without power.

At least 21 deaths have been blamed on the storm system since it charged out of the Plains during the weekend, piling snow in the Ohio Valley, producing mudslides and floods in the southern Appalachians, and making layers of ice that snapped trees and power lines.

The storm was headed for New England, where Massachusetts expected up to 2 feet of snow and minor coastal flooding.

Airports for Washington, Baltimore, Philadelphia and New York largely shut down, stranding thousands of passengers trying to leave and get into the region. Amtrak’s north-south service was halted between Washington and Richmond, Va., and regional bus service stopped in many areas.

The holiday meant there were few commuters, but police from Kentucky to Massachusetts pleaded with motorists to just stay home and some counties banned nonessential travel so they could clear the roads.

“This is going to be days’ worth of cleanup,” said Maryland Highway Administration spokesman David Buck.

The western tip of Maryland was buried, with 49 inches of snow in Garrett County on top of 30-foot drifts left by earlier storms.

“It’s no man’s land out there,” said Garrett County state highway supervisor Paul McIntyre, whose office window in Keysers Ridge, elevation 2,900 feet, was blocked entirely by snow. “It looks more like Siberia than Maryland.”

Elsewhere, 27 inches fell in West Virginia’s Berkeley County, the National Weather Service said. The Seven Springs ski resort area in western Pennsylvania had 40 inches. In northern Virginia, Winchester had 30 inches and Linden, on the Blue Ridge, measured 35. To the west, some parts of Ohio reported ice 8 inches thick with other areas under 16 inches of snow.

Ice also ravaged parts of Kentucky.

“All the trees are down,” Mark Caudill, 21, said at a shelter opened up in Lexington, Ky. “It looks like an avalanche just came through here and destroyed everything.”

It was one of the worst snowstorms in a century in Washington, where 16 inches fell. For the region as a whole, it was the worst snowstorm since the blizzard of 1996, when at least 80 deaths were blamed on the weather.

Among the many travelers stranded by the storm, few were as far from home as Lynn Anderson of Belfast, Ireland.

“It’s turned into a complete nightmare,” said Anderson, who arrived in Philadelphia on Sunday hoping to go to Williamsburg, Va., but had to stay overnight in a downtown Philadelphia hotel.

Staff members at Baltimore-Washington International Airport distributed blankets and pillows to the some 150 travelers who spent the night there. The Port Authority of New York and New Jersey, which operates Newark, Kennedy and La Guardia airports, supplied cots and blankets.

Thousands of travelers trying to get home from vacations were stuck at Florida airports.

“We are not going anywhere,” Elizabeth Huffman said at Miami International after finding her flight home to Washington was canceled. Her husband found an alternative: “We are thinking about going to the beach for the day.”

The heavy snow was blamed for several roof collapses in New Jersey, including one that killed a man at a job-training school in Edison. In Maryland, a train roundhouse roof fell in at the B&O Railroad Museum in Baltimore.

Ohio Gov. Bob Taft declared three southern counties disaster areas Monday because of the snow and ice. Disaster and emergency declarations also had been issued by governors in New York, Kentucky, New Jersey, West Virginia, Maryland and Delaware.

States had thousands of crews plowing and spreading salt. Maryland Gov. Robert Ehrlich said the storm had cost between $20 million and $30 million – and the state was already $14 million over budget for road cleanup this season.

New York Mayor Michael Bloomberg estimated the storm already had cost his city around $20 million.

It could take nearly three days to clear some side streets in Washington, said District of Columbia Mayor Anthony Williams.

“Once you’ve plowed this stuff, where do you dump these mountains of stuff?” Williams asked.

Usually bustling downtown Bethesda, Md., was nearly deserted, with sidewalks buried by snow. Jon Gann, 36, got out his snowshoes for a trek to a coffee shop. “This is great. I can walk on top of the drifts and completely avoid the streets,” Gann said.

More than 19 inches had fallen by afternoon in New York City’s Central Park, and the dense, fine flakes on unshoveled sidewalks made walking feel like a workout on a Stairmaster. Drifts stood chest high on some side streets and the Rockefeller Center skating rink was closed by snow for the first time since 1996.

An estimated 100,000 customers lost power in West Virginia, with 20,000 in the Carolinas, 62,000 in Ohio, 96,000 in Kentucky and 6,000 in Virginia.

“It’s by far the worst ice storm that we’ve had in decades. It’s a nightmare down here,” said Kimberly Carver, director of Ohio’s Scioto County Emergency Management Agency.

Weather-related deaths included two in Illinois, one in Nebraska, six in West Virginia, six in Missouri, one in Ohio, one in New Jersey and four in Iowa.

In Tennessee, two children were missing after the car in which they were riding was swept off a bridge by high water late Sunday. The car had not been found Monday. Their aunt, who was driving, was rescued.