WASHINGTON – One week after the nation’s capital experienced some of its worst flooding in more than a century, museums and other attractions were dried out and open for the long July Fourth holiday weekend.

Elsewhere in the Northeast, however, thousands of people were still trying to clear away flood debris and grime, or were still homeless after record flooding blamed for at least 20 deaths in Pennsylvania, Maryland, New York and Virginia.

On the National Mall, the 40th annual Smithsonian Folk Life Festival was open, attracting 80,000 people on Friday’s opening day.

As many as 500,000 people were expected Tuesday evening for the annual Capitol Fourth concert and fireworks display over the Washington Monument.

“We’ve dried out very nicely, and I have not seen any mud or anything, so we’re good,” said Becky Haberacker, a Smithsonian spokeswoman.

The Smithsonian’s National Museum of Natural History and the National Museum of American History were closed most of last week, primarily because of power failures associated with the flooding, but reopened Friday and Saturday.

Two other museums, the National Portrait Gallery and the Museum of American Art, held their grand reopening Saturday after six years of renovations in the Old Patent Office Building, which escaped flood damage.

The National Archives remained closed while experts dried out the basement.

Record flooding forced thousands of people to evacuate their homes over the past week in Maryland, Pennsylvania, New Jersey and New York state. More than a foot of rain fell last weekend around the Washington and Baltimore region.

The Delaware River between New Jersey and Pennsylvania had fallen below flood levels after inundating low-lying communities. At Phillipsburg, N.J., the Delaware crested Thursday at more than 14 feet above flood stage.

More than 200 people spent Saturday night in shelters across upstate New York, and uncounted others were still in hotels, motels and the homes of friends and relatives waiting for inspectors to give them permission to return home.

“It’s been so hectic here. We’re all kind of just running round for a report on how things are,” said Des Lambe, owner of the Reynolds House Inn in Roscoe, N.Y. He said he had two evacuee families scheduled to stay with him for the next week.

Others had been able to return and start cleaning up.

“It looks like people are shoveling snow, but it’s mud,” said Darcy Fauci, a spokeswoman for Broome County, N.Y. “Businesses are putting all their stuff in parking lots trying to dry it off.”

The federal government had declared eight New York counties disaster areas. One, Chenango, gave an early estimate of $32 million damage to infrastructure alone. Five other counties hoped to be added to the declaration.

New Jersey was still awaiting word on federal disaster aid Sunday. Federal Emergency Management Agency spokeswoman Jennie Raab said the request had been received, but FEMA and state officials were still assessing damage.