The National Museum of African American History and Culture sits near the Washington Monument. It opens Sept. 24. (Jahi Chikwendiu/The Washington Post)

THE MOST important thing about the new museum that opens Saturday in our city is not its bold architecture or the quality of its visual and aural exhibits or even the lessons it might seek to convey now and in coming years. The most important thing is simply that it’s here, at last, in the heart of the nation’s capital. One hundred and fifty years after the beginning of a hopeful national Reconstruction that was soon crushed to earth, a new structure stands on the Mall at the symbolic center of our country’s history: the National Museum of African American History and Culture.

In years to come, millions of Americans will visit this museum. They will be appalled by its presentation of the horrors of slavery; by the concrete, tangible evidence of state-sanctioned repression and the indignities that accompanied it; and by the illegal and atrocious acts of violence that persisted for a century after Emancipation. But they will also see and hear a story of accomplishment in the face of adversity and of resistance to injustices that were either inflicted or ignored by far too many Americans. There will be displays of brilliance, beauty, artistic achievement, military courage, religious devotion and just plain everyday life — a new light being shone on the story of people who were long neglected or disregarded.

Some critics who have seen the museum’s collections and exhibits have suggested that the picture presented is still too bright, given how much remains to be done to match American society to its stated ideals. Indeed, an updated museum might try, though probably in vain, to find some way to show a college professor’s anger and humiliation at being repeatedly pulled over while driving, or the absurd spectacle of an 80-year-old woman whose ancestors came to this country two or three centuries ago being denied the right to vote because she doesn’t have the papers to prove her citizenship.

But there is great power in what one will see at this museum, along with cause for hope. It is a truly national project, costing more than a half-billion dollars and funded in about equal measure by the federal government and private institutions and donors ($21 million from Oprah Winfrey, $5 million from Michael Jordan, $1 million from the Alfred Street Baptist Church in Alexandria). As the museum’s director, Lonnie G. Bunch III, put it in an interview with DeNeen L. Brown of The Post: “I want people to realize, this is who we are as Americans. I’m not creating an African American museum just for African Americans.”

Not far to the west of the museum stand the memorials to Abraham Lincoln and to the Rev. Martin Luther King Jr.; to the south and east, across the Anacostia River, is the home of former slave Frederick Douglass, who once said this: “In a composite nation like ours, as before the law, there should be no rich, no poor, no high, no low, no white, no black, but common country, common citizenship, equal rights and a common destiny.”

This new building will have served its purpose if it becomes a place for all the people who make up this composite nation to meet and to learn — to gain a better understanding of our past and to get to know one another a little better.