WASHINGTON — The hilltop mansion at Berkeley Plantation has a sweeping view of American history, if you’re still into that sort of thing.
English colonists settled the land along the James River a year before Plymouth and held one of the earliest recorded Thanksgiving celebrations there.
The three-story Georgian house, built by the Harrison family in 1726, was the birthplace of a US president and a signer of the Declaration of Independence. Taps was even composed at Berkeley 150 years ago during the Civil War, when Union soldiers used it as a base.
There is an abundance of history at the home. Visitors, however, aren’t so plentiful anymore.
Mirroring what’s happening to other historic house museums around the country, attendance is down 20 percent over the past five years at Berkeley Plantation, according to the national historic landmark’s private owner. The situation, he said, is bad and getting worse.
‘‘We’re scrambling right now,’’ said Malcolm Jamieson, whose father personally restored the property, about 30 miles west of Williamsburg, Va., then opened it to public tours several decades ago. ‘‘I think about the problem all the time. But I don’t know what to do.’’
Most house museums rely on admissions, gift-shop revenues, and donations to cover operating expenses. A few have substantial endowments or receive government funding. But not Berkeley Plantation, where Jamieson cut his salary and has been hosting more weddings and corporate events just to stay afloat.
There are hundreds — if not thousands — of house museums around the country, though nobody knows exactly how many. Virginia is particularly rife with them, given its central role in American history, from Colonial times through the Civil War.
The state has counted more than 100 homes in the Commonwealth that are open to the public as historic sites and museums, and it will soon start promoting them: Governor Robert McDonnell has proclaimed 2013 the year of Virginia historic homes, in part to celebrate the Executive Mansion’s bicentennial but also to call attention to the state’s other house museums.
‘‘We all know of Monticello and Mount Vernon, and they’re fabulous,’’ said Sarah Scarbrough, director of Virginia’s Executive Mansion. ‘‘But there are so many other homes in Virginia, and they’ve been struggling. The severity of the problem is alarming.’’
The issue isn’t exactly a new one for the old homes; most house museums have been reporting slides in attendance since 1976, when America turned 200 and interest in US history spiked.
That year, Thomas Jefferson’s Monticello welcomed a record 671,000 visitors; in 2011, attendance at the Charlottesville estate was 440,000.
Economic forces are partly to blame. Tourists aren’t traveling as much because of gas prices and shrinking discretionary budgets. School systems — which send kids to historic homes to bring the past alive — aren’t funding as many field trips.
‘‘Which is a shame,’’ Scarbrough said. House museums, she said, are cultural assets that help people understand the heritage of their communities and the country, providing context and rich detail about people, places, and periods.
But several of Virginia’s house museums, which were once open daily, have cut back to four, three, or even one day a week, Scarbrough said. There’s been talk that a few of them might be closing for the winter — and there’s concern that some might close their doors for good.
It wouldn’t be the first time.
Twelve years ago, General Robert E. Lee’s boyhood home in Alexandria, Va., was sold because the nonprofit foundation that owned it couldn’t afford its upkeep as a museum. The buyers — venture capital executive Mark Kington and his wife, Ann — turned the historic treasure into a private residence.
Some preservationists and historians are pushing for house museums across the country to merge their operations, said Kenneth Cohen, the museum studies program coordinator at St. Mary’s College of Maryland. The idea hasn’t been warmly received.
‘‘Institutions are generally reluctant to give up their autonomy,’’ Cohen said. ‘‘The result is that lots of small historic houses are teetering on failing — and closing.’’