Donald Trump's new hotel is not the most important new building on Pennsylvania Avenue – whatever he tries to tell you

No one could have predicted things would come together like this – those many years ago when plans to realise an African-American dream finally took wing, and more recently in 2011, when a flashy Manhattan property tycoon put in a bid to turn a grand old building on Pennsylvania Avenue into the latest in his line of branded luxury hotels.

But history’s lines move in mysterious ways. For the US capital, this September of 2016 is a tale of two openings, a few blocks and a few days apart. And somehow, the two unrelated and utterly contrasting events are a snapshot of the polarised state of the country, seven weeks before America’s nastiest and highest stakes election of modern times.

Act One took place a lot more quietly than you would have expected. The Trump International Hotel opened its doors to business last Monday without fanfare, in the Old Post Office Pavilion – right on the presidential inaugural parade route, just half a dozen blocks from the White House that its controversial proprietor could be moving into early next year.

Given all that, it was striking that only a couple of dozen protesters showed up, bearing motley banners proclaiming things like “Trump’s A Racist,” and “Love Trumps Fear.” It was a hot sunny day, and the few police on hand sat on benches, checking their phones. The real story was inside: the razzle-dazzle Trump décor, the $600-a-night rooms ($1,000 for inauguration week), the champagne bottles opened by sabres, the super-fancy wines guests can purchase by the spoonful.

This isn’t your usual high-end Washington hotel, all dark panelling and discretion, where you might spy an ex-director of the CIA at a quiet table in the bar, catching up on gossip with friends. This place makes a statement about a new Washington. Not so much about the new Washington that would undoubtedly be under a Trump administration – but of the New Washington that has been taking shape these past two decades: whiter and richer, a city of business almost as much as government. A more Trumpian city if you like – even if the man himself doesn’t win in November.

And now to Act Two. The seed was sown back in 1915 when a group of black veterans who had fought on the Union side were in Washington for the 50^th anniversary celebrations of the Civil War’s end and were disgusted by how little had changed, despite emancipation. They decided to set up a “coloured citizens’ committee,” to press for an exhibit that would showcase how much blacks had contributed to America.

But nothing happened. Pilot schemes came and went. Racism was one reason, as old-guard southern politicians argued that to give African-Americans a national museum would mean everyone – Hispanics, Asian Americans, you name it – would want their own spot on the Mall, their own little tent on what has been described as America’s front lawn.

In the meantime a museum of the American Indian opened in 2004, not to mention the Holocaust Museum (not part of the Smithsonian stable, to be sure, but which has been in place since 1993), dedicated to an event that had taken place thousands of miles from US shores. But a memorial to set out the long, often tragic history of black Americans – among the very first Americans, whether they liked it or not – from slavery to the modern day? Still nothing.

The pressure however continued, and in 2003, President George W Bush finally signed a Congressional act setting up the National Museum of African American History and Culture (or NMAAHC if you’re into clumping acronyms). Work at the site, the last available for a museum bordering the Mall, started in 2012. It opens on Saturday, 24 September, 12 days after Trump’s hotel. And this time, by contrast, there’ll be a very great deal of fanfare indeed.

Leading the ceremony, fittingly, will be Barack Obama, the first African-American president. There will be days of festivities, while entry tickets to the museum (free like all the Smithsonian ones) are sold out until November.

The building’s been worth the wait, elegant and graceful, constructed in the shape of three crowns on top of each other, covered in a black lattice. When it was put up in 1899 to regenerate an area riddled with crime and prostitution, the Post Office Pavilion – at the time the second tallest building in DC behind the Washington Monument – was a ground- breaker. NMAAHC, a gorgeous addition to the Mall, will be another.

The architectural concept is a climb out of darkness, beginning with the era of slavery and oppression, set deep underground, up through sections dealing with Jim Crow and the long struggle for civil rights, to the topmost floor and a celebration of black culture. The exhibits, collected from scratch, reflect the long historical march of black America: from an early 1800s slave cabin to the open coffin in which lay Emmett Till, the 14-year-old boy savagely murdered in 1955 in Mississippi for whistling at a white woman. Photos of Till’s disfigured body helped galvanise the embryonic civil rights movement.

But gradually the mood lightens. You move on to the great breakthroughs of the civil rights era, the increasing prominence of black people in national life, and their cultural achievements. Illustrating them are items like General Colin Powell’s military uniform, the head protector Muhammad Ali used while sparring, and Chuck Berry’s red Cadillac, as well as an exhibit on Duke Ellington, the jazz great who may be Washington DC’s greatest son.

You can say the museum tries to cram too much in. You might cynically argue the whole thing is little more than an exercise in feel-good politics, designed to project an America racially at peace with itself, despite the police killings of unarmed black men, the riots in cities like Baltimore, and the emergence of the Black Lives Matter movement. But it’s a mirror of a real America nonetheless – as is, in its in-your-face fashion, that garish new hotel a few hundred yards down Pennsylvania Avenue. Whatever happens on 8 November, the twain shall never meet.