A landmark in history: Martin Luther King Jr Memorial

Natural disasters permitting, tomorrow will see the opening of Washington DC’s newest monument.

It is a walk of barely 200 yards, an easy stroll even in the heat – down the steps of the Lincoln Memorial and past the ghostly soldiers of the Korean War Veterans Memorial to 1964 Independence Avenue, where the new pedestrian crossing is still being daubed across four lanes of traffic. Physically, the journey takes me five minutes, maybe six. In other ways – politically, spiritually, sociologically – it has taken many people far longer.

For it is here, tomorrow, that (hurricanes and earth tremors notwithstanding) Washington DC's newest landmark, the Martin Luther King Jr National Memorial, will be opened by President Obama, on the 48th anniversary of the civil rights leader's seismic "I Have A Dream" speech – and practically within audible range of the spot where he delivered it, under Abraham Lincoln's statuesque gaze.

Not before time, either. It is no outlandish claim to say that the arrival of an official site dedicated to the civil rights struggle in the US capital is long overdue. The National Mall – that hallowed strip that runs east-west through the centre of Washington – already pays tribute to several of the causes the country has battled for in its young history, from the fight for nationhood, to the Second World War. But its bleakest hours are notably absent. When Obama pulls back the curtain tomorrow, there will be a sense of an oversight being corrected.

The ceremony will be a momentous event. This will be the first personal memorial on the Mall built to honour someone other than a former president. As many as 400,000 spectators are expected to mark the occasion – the largest gathering on the Mall since the current commander-in-chief's 2009 inauguration. Washington may grind to a halt.

If it does, it will not be for the first time this week. The images of locals running into the streets during Tuesday's earthquake were as remarkable as they were unexpected. The 5.8-magnitude tremor was strong enough to damage one of the spires on the National Cathedral – although plans for tomorrow's memorial dedication were unaffected.

Even before the earthquake, there is a strange, indefinable turbulence on the air the week I visit. Perhaps it is the summer humidity, perhaps the fact that the sabre-rattling ahead of next year's presidential election has begun. But the traffic snarls past the Washington Monument. The Reflecting Pool below the Lincoln Memorial is a muddy scar, midway through a restoration process that has seen it entirely dismantled.

Even the souvenir stalls by the White House are trading in contradiction – T-shirts that either weep for a beatific-looking Michael Jackson or hail the death of the world's most infamous terrorist with the line "Osama Got Obama'd".

Yet all this fades as I approach the new memorial. A palpable peace hangs over the site – even as construction workers make adjustments to the adjacent information centre. Created by the Chinese sculptor Lei Yixin, the monument offers a literal take on a single quote from King's most famous speech: "With this faith we will be able to hew out of the mountain of despair a stone of hope." Visitors enter through a passage between two giant chunks of pink granite (the mountain of despair) to find the man himself emerging in relief, 28ft tall, from a third block (the stone of hope) – and staring south across the Tidal Basin, to where the presidential memorials to Thomas Jefferson and Franklin Delano Roosevelt lie.

The alignment is deliberate. "The site was carefully identified," explains Mieko Preston, one of the architects behind the project. "It sits in a direct line between Lincoln – the man who kept the United States united – and Jefferson – who drafted the Declaration of Independence. It is the logical place for the memorial. It is a straight line of leadership." The significance of the proximity to Jefferson becomes obvious later in the day when I amble around the Tidal Basin, and find the third US president's most iconic words etched into the wall of the neo-classical temple that celebrates his life: "We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain inalienable rights, that among these are life, liberty and the pursuit of happiness." With the King memorial visible in the background, they ring with new clarity.

But first there are the quotes on the King memorial itself, 14 of them, taken from books and speeches, cut into a 450ft wall behind the main sculpture. Some are defiant: "We shall overcome, because the arc of the moral universe is long. But it bends toward justice." Some are hopeful: "We must come to see that the end we seek is a society at peace with itself, a society that can live with its conscience." Some are poetic: "Darkness cannot drive out darkness, only light can do that. Hate cannot drive out hate. Only love can do that."

One is missing.

Mieko Preston smiles. "There is no need to quote 'I have a dream'," she says, glancing to her left, perhaps towards the White House. "Because that dream has been realised."

Getting there

* The writer travelled to Washington with Virgin Atlantic (0844 209 7310; virgin-atlantic.com), which flies daily from Heathrow to Washington's Dulles daily from Heathrow in competition with United (0845 844 4777; unitedairlines.co.uk) and British Airways (0844 493 0787; ba.com). BA also flies from Heathrow to Baltimore-Washington.

Visiting there

* Martin Luther King Memorial, 1684 Independence Avenue SW ( mlkmemorial.org). Open daily from 29 August, free.

Staying there

* Hotel Monaco, 700 F Street NW (001 202 628 7177; monaco-dc.com). Double rooms start at $388 (£237), room only.

More information

* washington.org

* capitalregionusa.co.uk