It's been a long time coming, almost a century in fact. But Washington's National Mall, home to unarguably the greatest concentration of museums on this planet, will soon be filling in the one glaring omission from that fabulous collection: a national museum celebrating black history and culture.
Critics have long complained that the Mall is overcluttered. But over the 20-odd years I've lived here, the "clutter" at America's glorious outdoor drawing room has only grown. Since 1991 a Korean War monument, a Second World War monument and a memorial to President Franklin D Roosevelt, as well as a National Museum of the American Indian and a National Holocaust Museum whose subject, however harrowing, is at most tangential to US history, have all arrived. But no museum about black history.
They've talked about one many times, of course. The first effort to create one came in 1915, when a group of black veterans campaigned for a memorial. Small hope: that was when Jim Crow ruled the South, and the very year when, inter alia, D W Griffith produced his wildly popular but unabashedly racist silent movie classic The Birth of a Nation, glorifying the Ku Klux Klan.
Several subsequent attempts also foundered, even one after the passage of the landmark 1960s civil rights legislation. Sometimes the resistance was passive, sometimes less so – as when the race-baiting Senator Jesse Helms of North Carolina railed against the project. "Once Congress gives the go-ahead for African Americans," he declared, "how could Congress then say no to Hispanics, to the next group and the next group after that?"
But Helms retired in 2002, and the following year Congress did give the go-ahead. A director was appointed and a location approved for the museum-to-be, barely 100 yards from the Mall's centrepiece, the 550ft-tall white marble Washington monument. Cluttered the Mall may be, but a site anywhere else would have been construed as yet another injustice visited upon America's black population.
Preliminary clearing work has begun, and the $500m project, paid for half by the government, half by privately raised funds, is due to be completed by 2015 – when, if Barack Obama is re-elected, an African-American president will fittingly cut the ribbon at the opening ceremony. In another sense, however, the difficulties are only beginning.
The place was always going to be controversial. Whichever way you cut it, this 19th (and perhaps last) museum in the Smithsonian complex will deal, explicitly or implicitly, with race, an issue that has lost none of its sensitivity with Obama in the White House.
Only last year Washington went into temporary meltdown over Shirley Sherrod, the black Agriculture Department official wrongly ordered to resign over remarks, taken out of context and misleadingly edited by a right-wing group, that she had once racially discriminated against white farmers in Georgia. Then there was the furore over the arrest in 2009 of the eminent black Harvard historian Henry Louis Gates, into which the President himself unwisely stepped. The handcuffs used by the white police officer have been donated by Gates to the museum.
So what will it focus on? In a word, everything – from the misery of slavery to the heroism of the civil rights movement, to the colossal contributions of blacks to American music and culture, art and sport. But it will not be a museum specifically for African Americans, says Lonnie Bunch, its director.
"This will be a national museum telling an American story," a story that affects all Americans, explaining not just how America shaped blacks, but also how blacks helped to shape America. Mr Bunch wants to use the vast recent scholarship on the subject to "contextualise" that story, and show "how America is a work in progress, how the civil rights struggle has been going on ever since we've been a country".
Another and more practical problem is that the museum has come about so late in the day. Its collection already consists of 11,000 pieces, either bought or donated, and Mr Bunch wants to double that total before the 2015 opening. But many of the most significant objects are on display elsewhere around the country, in hundreds of history museums – and not only black history museums – already in existence.
Take the whites-only lunch counter from the Woolworths store in Greensboro, North Carolina, where four black students staged their famous sit-in in 1960. The store itself has been preserved as a civil rights museum, while a segment of the counter is to be found in none other than the National Museum of American History – right next door on the Mall to where the National Museum of African American History and Culture will stand.
The US is full of amazing black museums, some in buildings of intense historical resonance. Take the Lorraine Motel in Memphis, now the National Civil Rights Museum: its centrepiece is Room 306, on the balcony of which Martin Luther King was standing when he was shot on 4 April 1968, left as it was that fateful evening. Another is the Civil Rights Center in Birmingham, Alabama, opposite the 16th Street Baptist Church bombed by KKK men in 1963, when four little girls were killed in an atrocity that stunned the country.
On a more uplifting note, there's the Muhammad Ali Center in the great boxer's hometown of Louisville – or the nondescript two-storey house at 2648 West Grand Boulevard in Detroit, where Berry Gordy launched one of the most famous record labels in history, now the Motown Historical Museum.
But Mr Bunch is using ingenious means to fill the gaps. The New York Times reported last week how curators are holding Antiques Roadshow-type events around the country called "Save Our African-American Treasures", aimed at bringing to light unsuspected historical artefacts.
At one in Detroit last year, for instance, a retired clerk produced poll tax slips paid by her grandfather between 1900 and 1908 – exceedingly rare documentary evidence of the levy used in southern states to prevent poor blacks from voting, a practice finally banned by the Supreme Court only in 1966. Of such small jewels are great museums made.