The American Revolution was fought in a climate of anticipation. Enlightened thinkers around the world hoped that America’s new spirit of freedom would unleash a political, economic and cultural renaissance.

“A new Greece will perhaps give birth on the continent … to new Homers,” predicted the Abbé Raynal, the French philosophe. Horace Walpole speculated: “The next Augustan age will dawn on the other side of the Atlantic. There will, perhaps, be a Thucydides at Boston, a Xenophon at New York, and, in time, a Virgil at Mexico.”

It didn’t end up quite that gloriously. Many of the 18th-century figures assumed that economic growth and cultural genius were part of one thing — progress — and that in an atmosphere of freedom they would rise together. But in America it became clear that commerce and culture were different things, and that while commerce surged, culture lagged.

Before long, people noticed that the United States had become divided into, as Van Wyck Brooks put it, “two publics, the cultivated public and the business public, the public of theory and the public of activity, the public that reads Maeterlinck and the public that accumulates money.”

Still, throughout the 19th century these two publics did at least talk to each other. Both were obsessed with one subject: the meaning of America. Whether they were tycoons, politicians, theologians or artists, Americans of the 19th century tended to assume that history had a storyline, and that the United States had a distinct and climactic role in its unfolding.

Much of the conversation was about America’s meaning and providential role. And this conversation is the subject of two fantastic museums that are reopening Saturday, after six years of renovation, in Washington.

The National Portrait Gallery tells the story of American history through its great personalities. The Smithsonian American Art Museum tells the story of its art. Through an accident of history, the two museums share a single building, the old Patent Office Building, which Walt Whitman called the noblest building in the city.

The museums have always existed uneasily together. Six years ago, the curators of the Portrait Gallery were furious because the Art Museum was taking advantage of the renovation to seize most of their building’s best spaces. And even Tuesday, as the directors of the two museums led me around, there were moments of awkwardness, as they vied over tour routes, interpretations and which museum’s tote bag I would use to hold the press materials.

But for the regular visitor, the end product is exhilarating. What you see within these two museums’ interlocking spaces is the great conversation about the American identity. Here in the Art Museum are George Catlin’s dignified portraits of Indians; there in the Portrait Gallery is a defiant bust of the Indian-fighter, Andrew Jackson. Here’s an elegant painting by John Singer Sargent; there’s a portrait of a slovenly P. T. Barnum. Here’s a W.P.A. mural celebrating harmony and plenty; there’s a portrait of the Scottsboro Boys.

There are jarring transitions between the two museums. And it’s weird to be in a building with dueling narratives. But this is the cacophonous reality of America.

The building’s finest spaces are on the third floor, where the two museums hold their material from the past 50 years. A lot of great stuff is there — including a mesmerizing David Hockney installation — but the conversation stops. The two museums no longer reverberate against each other.

That’s because around 1960 the art world and much of the intellectual world lost faith in the idea that history has a storyline and that America has a distinct role in it. This week, Blake Gopnik spoke for the art establishment in his review of the museums in The Washington Post, arguing that there is no essentially American culture — no transcendent thing we Americans share simply because we happen to inhabit the same nation-state.

So the artists have gone off to have a conversation about themselves. But most people who tour these museums will feel a transcendent thing called Americanness deep in their bones. They will understand what George Orwell meant when he said your country “is your civilization, it is you.” And today, when America is unpopular and the whole concept of Americanness is encrusted with clichés and conspiracy theories, they’ll feel thrilled to get back and touch the real America, the real conversation, which has been so triumphantly presented in the old Patent Office Building in downtown D.C.