(Katie Vernon/For The Washington Post)

Art museums are public spaces, but they are not necessarily social spaces. You can still be alone in the crowd, still find some spot antipodal to the “Mona Lisa” where the lonely art wants your solitary attention. History museums, increasingly, are about interaction with others, carefully engineered experiences that connect you to other people, and ideals of collective identity. And no type of museum is more social than the presidential house, that hybrid of the sacred and domestic space where the authentic man is conjured up by perky tour guides herding their motley flocks.

Once a necessity — how do you accommodate a million visitors a year in a house built to 18th-century scale? — the tour with narration has become an essential and, for many, a beloved part of the experience. From this random assemblage of tourists, curious affections and resentments can blossom among strangers even in an hour. In the drawing room of old slave masters and the gloaming of humble wooden homes, the basic tourist types show their colors: The earnest reader of biographies who wants you to know he has done all his homework; the contrarian muttering loudly to spouse and children; the one-issue evangelist with very peculiar views on slavery and the Civil War; and the domestic diva (of either gender) who won’t shut up about the lack of closet space.

The history of presidential sites isn’t just a matter of preservation or archaeology. It is a social history, too. The inclination to preserve houses or other sites closely associated with the Founding Fathers begins about 1850, not surprisingly as the ranks of the last living veterans of the Revolutionary era were disappearing. In 1850, the governor of New York, Hamilton Fish, persuaded his state to preserve the Jonathan Hasbrouck home in Newburgh, where Washington had his headquarters from 1782-1783, making it the first publicly owned historic site in the nation.

A few years later, a Southern woman passing by the dilapidated Mount Vernon proposed preserving it as an act of feminine patriotism: “Why was it that the women of this country could not try to keep it in repair, if the men could not do it?” Her daughter, Ann Pamela Cunningham, founded the Mount Vernon Ladies’ Association, an organization with a decidedly Southern sensibility that also was the first national preservation organization in the country.

Both of these early acts of historic stewardship have analogues in the family drama: The urge to preserve and construct memories of our forebears as their living presence fades into history, and the urgent desire to find or fashion a common sense of history as the national family was being torn asunder by the shame of Southern slavery.

It was never about just preservation. The passion for Colonial history in the late 19th century was part of the larger project of Gilded Age social control, a mix of aesthetics and mythology meant to inspire the masses­ to more regulated, productive and compliant participation in the economic and political life of America. As the great American family grew more ambitious, fractious and diffuse, and felt threatened on all sides in the 1920s and 1930s, its need for shrines was so powerful that it didn’t bother with history or authenticity. In 1930, the George Washington Birthplace house in the Northern Neck of Virginia was constructed ex nihilo based on 18th-century precedents but no actual physical evidence. The real one had burned down in 1779, and its remains were found a few years after the imagined one was finished.

The unembarrassed reverence of the Founding Fathers that sought outlets in manufactured history changed over the years, as historians and the public grappled with the complicity of the country’s first politicians in the great original sin of the nation. Historic sites also became more professional, and visiting them offered more substantial and eventually nuanced history, and less home-decorating tour. In the 20th century, as academic historians diverged from popular history, presidential homes followed the latter, focusing on fantasies of “the authentic man,” and the great leader “at home,” dependent on narrative and anecdote to make long-dead political leaders seem more approachable and engaging.

Today, the best presidential sites are stalwart forces­ for telling history against the grain of the virtual, disembodied world of online and digital life. They not only force us to encounter the tangible stuff of built and made things, but also strive to cut through the aggregated tribalism of American political life. We self-sort online, choose our friends from the same social, political and partisan pools, and frequent churches, bars, restaurants and sporting events where we are certain of finding like-minded people — or having no occasion to discover otherwise. But touring Monticello puts you in inescapable contact with those mysterious and invisible people who vote for the other party.

As presidential sites have turned to tour guides who act as professional interlocutors, forcing people to answer questions and engage with one another’s responses, they have become one of the last safe places for genuine encounters with the Great American Other. It is a tense, sometimes awkward and often painfully weird experience, and it all happens within the walls of someone else’s house. They may no longer be the bearers of the myths and emotionalism of our former reverence for great leaders, but the presidential site gets at the heart of the current, slightly exhausted, nervous moment of the family drama: the vexing sense that, for better and worse, we are all in this together.