Rupert Cornwell: He had a dream – and now it's set in stone

Out of America: The figure of Martin Luther King stands 30ft high, in a monumental tribute to his stirring reconciliation speech made 48 years ago today

The new Martin Luther King memorial will be dedicated by President Barack Obama (afp/getty images)

In terms of physical damage and devastation, Hurricane Irene may have a great deal to answer for. But here in America's capital, to injury has been added insult. The storm has forced the postponement of today's planned formal inauguration of the new memorial to Martin Luther King on the National Mall in Washington DC. The dedication was to have been performed by the black president whose own miraculous ascent and inauguration would never have happened but for Dr King and the movement he led, and the speech he made close to that spot exactly 48 years ago.

Despite its sylvan setting on the banks of the Tidal Basin, where in springtime tourists come to admire the blossoming cherry trees, there is something jarring about the structure. And that is exactly as it should be. King's speech was a soaringly beautiful cathedral of language, but also a rude call to action.

You cannot but be struck by the monument's layout, that gives form to King's words that day. You approach by a path cut through two mounds of rock, a 30ft tall "mountain of despair". Set in front of them is "the stone of hope", hewn from the space where the path now runs. From the "stone" emerges the sculpture of the subject, his arms folded in front of him. If size is the measure of importance, King is indeed monarch of the Mall. His effigy stands midway between the monuments to Abraham Lincoln and Thomas Jefferson, but their statues are both only 19ft tall.

Some have objected that King is gazing at Jefferson, rather than Lincoln – at a president who owned slaves, not at the one who emancipated them. But that, too, is surely as it should be, a symbol of the reconciliation which he evoked on 28 August, 1963; that "one day on the red hills of Georgia, the sons of former slaves and the sons of former slave owners will be able to sit down together at the table of brotherhood".

For black America, moreover, today's date is doubly charged. It is, of course, the anniversary of King's speech. But on the very same day eight years earlier, there occurred the dreadful incident that perhaps more than any other opened the country's eyes in shock to what was still happening in the South, nearly a century after slavery was officially abolished.

Emmett Till was a 14-year-old black boy from Chicago visiting relatives in the Mississippi delta. He was accused of speaking flirtatiously to a married white woman and on 28 August 1955 was dragged from the tiny house where he was staying, and savagely beaten and murdered. His killers weighed down his body by tying it with barbed wire to a cotton gin fan, and then dumped it in a river. A month later the woman's husband and an accomplice were put on trial for the crime, but despite overwhelming evidence of guilt they were acquitted – a verdict so outrageous that it galvanised the civil rights movement, of which King would emerge as leader.

But the mere dedication of a monument does of itself not turn wrongs into rights, or wipe a country's conscience clean. Yes, the new King memorial is remarkable: the Mall is a place that honours wars and those who died in them, and the country's greatest government leaders. Yet King was a pacifist (and widely reviled for it). He was an outsider, who made his reputation by defying the laws of the land.

He preached reconciliation, but as Cornel West, a Princeton professor and leading African-American intellectual, argued in The New York Times on Friday, King was also a revolutionary, who never ceased to decry the "racism, poverty, militarism and materialism" of American society.

Racism still exists here, as in every country on earth; it is far easier to change laws than attitudes. Look no further than the lingering de facto residential segregation of cities like this one, or the gross over-representation of blacks in the general prison population and on death row. But there could be no greater proof of the progress America has made in overcoming its original sin than the election of a black man to the presidency, just 45 years after King's speech.

If he were alive, King would be immensely proud, and probably utterly astonished, at the achievement. But American materialism and militarism are undiminished. As for poverty, who needs reminding of the gulf between rich and poor, a divide that has only deepened amid the economic crisis?

Note the formal title of the August 1963 event, the "March on Washington for Jobs and Freedom". Yes, the gigantic rally was to protest America's failure to deliver on its constitution's promise of equal treatment and opportunity for all, whatever their race or skin colour. But it was also about the economy, and what was then, and remains today, its most relevant barometer for ordinary people: Do I have a job?

Neglected amid the poetry of King's speech was the accountant's language with which he began it. The US he said, "has given the Negro people a bad cheque, a cheque which has come back marked 'insufficient funds'." Now, he went on: "We've come to our nation's capital to cash a cheque." But have they managed to, 48 years later?

Since the 2008 crash, blacks have gone backwards economically. Since George W Bush left office, black unemployment has risen from 11 per cent to nearly 16 per cent, compared with an overall national rate of just over 9 per cent. According to one recent study, the median wealth of black households is one-twentieth of that of white households.

In 1963, King declared that the March on Washington was not an end but a beginning, and so it proved. The same goes for the new memorial, a reminder not of what has been achieved, but of what remains to be achieved. It would have been wonderful to hear President Obama unleash his eloquence on this unfinished business. But now we must wait at least until September – thanks to Hurricane Irene.