By Kevin Connolly
BBC News, Washington
Mr Obama carries a heavy burden from the past on his shoulders
With every step he took along the journey that has now led him at last to the White House, you sensed that history was shadowing Barack Obama, never more than a half a pace behind him.
From the moment at the Democratic Convention in Boston in 2004 when he first displayed his extraordinary ability to conjure a mood and capture an audience, it began to seem possible that he would prove himself the first black man with a realistic chance of winning the White House.
From that moment on, he was written about and judged in a way that set him apart from the other candidates who crowded America's political stage in the early months of Campaign 2008.
Because of the colour of his skin, Mr Obama was not merely another primary candidate - he was a character in the long and painful story of America's evolution away from a past of racial division and violence.
Not since Robert Kennedy's doomed run for office in 1968, perhaps, had a candidate with a realistic chance of victory entered a presidential race carrying such a burden from the past - although Kennedy's burden was, of course, very different.
Message from Lincoln?
Mr Obama seemed to sense it too - his speeches were littered with allusions to history, because he understood that you cannot shape the future unless you understand the past.
Mr Obama swore the oath of office on former President Lincoln's Bible
We hear a lot about Mr Obama's fascination with America's 16th President Abraham Lincoln, that other man of Illinois who appeared at a moment of national crisis to win a civil war to abolish slavery.
Is there in that fascination perhaps a message? Lincoln may have been on the side of the angels, but he was a tough pragmatist rather than a dreamer and he was prepared to do whatever it took to save the Union, win the war and free the slaves.
Will Mr Obama turn out to be a similar kind of figure - tough in pursuit of a few key policy goals and ready to do whatever it takes to deliver them?
We will see - for the moment the historical resonances of the Lincoln years have been a little more subtle than that.
The inaugural lunch was composed of dishes like seafood stew, that Lincoln is known to have liked, and it was served on crockery in a shade called Solferino - a peculiar mauvish shade which was the last word in interior design around the 1860s.
Intriguingly, it was a quote from Thomas Paine that was borrowed by America's founder and first president, George Washington, which caught the eye in the inaugural address, rather than anything which echoed Lincoln.
It came from the depths of a winter when Washington's revolutionary army seemed to be on the point of defeat at the hands of the British: the great general summoned his nation to arms, calling on his people to prove to history that at a desperate moment they rose to meet a common challenge.
Mr Obama built on the quote, inviting future generations to judge his leadership, saying: "Let it be said by our children's children that we refused to let this journey end."
The problem is that there's no guarantee that having a sense of history guarantees that you will be judged kindly by it.
George W Bush is said to be an avid reader of historical works too - and to share Mr Obama's fascination with Lincoln - and yet he is leaving office with a curious atmosphere of melancholy clinging to him because his period in office cannot possibly have turned out as he hoped.
Mr Obama is unusual because he will be written about by future historians in two different ways.
First, there will be the question of how he uses his power to shape history.
Many will look to see how prospects for African-Americans change
His inaugural address while it perhaps lacked one single line that will resonate down the ages, was a masterpiece in the sense that it sought to lift America's hearts in the moment, whilst also lifting its eyes to the scale of the challenge ahead.
The challenges won't be met quickly, or easily, but: "America, they will be met." There you have the yardstick against which Mr Obama invites judgement - realistic in his assessment of the difficulties ahead and yet prepared to dream when he imagines America's future.
The second way in which he will be judged, of course, is for the manner in which he fulfils that role as a character in the story of America's painful evolution into a society where hope and opportunity are shared equally between black and white.
There are any number of statistics which illustrate how unequal things are now, more than 40 years after Martin Luther King spoke of a dream which embraced not just racial equality but an end to poverty too.
A civil rights activist in the South told me, for example, that young black men in America are more likely to go to prison than to college.
Mr Obama enjoys overwhelming and deeply emotional support from nearly all African-Americans, who see his triumph as a triumph for all of them.
The inaugural ceremony took place at a building built by slave labour
Nothing will dim their support for him - love is not too strong a word - but historians of the African-American experience will judge his time in office by how the lot of black Americans changes on his watch.
It is a tall order, but he has plenty of change to build on. As he said himself, he is taking office in a city where his father wouldn't have been allowed to book a restaurant table, and that is extraordinary enough.
And he swore his oath at a Capitol building which was the work of black slave labour - those nameless figures from the bigoted past must have watched the day with silent acclamation too.
We will see what Mr Obama does with the history which is now his to shape - but the history he embodies is already written and his place in America's remarkable journey, in that sense at least, is already assured.