emphatically chosen Barack Obama as their first black president in an election
that promises to reshape US politics and the superpower's role on the world
As he wrote himself into the history books, the Democrat leader told 240,000 euphoric supporters in his home town of Chicago that his victory proved anything was possible.
Flanked by his family, Senator Obama told the sea of supporters it was time to reclaim the American dream.
"If there is anyone out there who still doubts that America is a place where all things are possible; who still wonders if the dream of our founders is alive in our time; who still questions the power of our democracy -- tonight is your answer," he said.
"Change has come to America."
Senator Obama, 47, will become the 44th US president when he moves into the White House on January 20.
The son of a black man from Kenya and a white woman from Kansas, he told the crowd "this victory alone is not the change we seek. It is only the chance for us to make change".
President-elect Obama inherits an economy mired in the worst financial crisis since the 1930s, two wars in Afghanistan and Iraq, and a nuclear showdown with Iran.
"The road ahead will be long; our climb will be steep. We may not get there in one year or even one term, but America -- I have never been more hopeful than I am tonight that we will get there," he said.
"I promise you -- we as a people will get there."
He also vowed to be a president for all Americans.
Hundreds of thousands of teary-eyed and jubilant supporters witnessed the new dawn of American politics.
Senator Obama's smile was broad, but his face also reflected the powerful emotion of the occasion.
He thanked his wife, Michelle, and told his daughters Malia, 10 and Sasha, 7, they had earned "the new puppy that's coming with us to the White House".
His triumph was greeted with euphoria across America and reverberated around the world.
New York's Times Square exploded in joy at a moment of healing for America's racial scars, and a crowd gathered outside the White House.
Senator Obama smashed a colour barrier in a way that was unthinkable a generation ago, when the Deep South was segregated and blacks were banned from voting.
Pessimistic about the crisis-ridden US economy, a record number of voters embraced a sweeping national mood for change, painting the American electoral landscape blue for the Democrats.
Riding a wave of energised first-time voters, Senator Obama swept through America's heartland, winning the working-class battlegrounds of Pennsylvania and Ohio right through to the western state of Colorado.
On a night when his gutsy Republican rival John McCain held on to a swag of southern conservative states but ran out of comebacks, Virginia fell to the Democrats for the first time since Lyndon B. Johnson's 1964 landslide.
Senator Obama trounced his adversary in major battlegrounds and poached states long considered to be Republican bastions.
He sealed his overwhelming victory by taking back Florida, the state that broke Democrat hearts in the court-contested election of 2000 between Al Gore and George W. Bush.
Several US news networks reported the popular vote as relatively close -- CBS called it 52 to 47 per cent -- after more than 104 million votes had been counted. A handful of states were still to report their results.
But in terms of the all-important Electoral College vote count, it was a blowout.
When counting stopped for the night, Senator Obama had secured an estimated 349 electoral votes compared with 162 for Senator McCain.
The candidate who reaches the threshold 270 out of 538 electoral votes nationwide is declared the winner.
It was the first time since Jimmy Carter in 1976 that a Democrat won the White House with more than 50 per cent of the popular vote.
Unlike the cliffhangers of the past two elections, the results unfolded quickly.
As soon as US networks called Pennsylvania for Senator Obama, tens of thousands of his supporters crammed into Chicago's sprawling Grant Park to watch big-screen TVs.
The euphoria exploded when Virginia fell, as supporters with tear-stained cheeks screamed, cheered, danced and chanted "Yes, we can".
After calling Senator Obama to congratulate him on becoming president-elect "of a country we both love", Senator McCain spoke to his supporters in Phoenix, Arizona.
"This is an historic election, and I recognise the special significance it has for African-Americans and for the special pride that must be theirs tonight," he said.
Senator McCain also thanked his controversial running mate, Alaskan Governor Sarah Palin, describing her as "an impressive new voice in our party".
President George W. Bush congratulated Senator Obama on his "awesome night".
And Democratic rival Senator Hillary Clinton promised her full support.
"American voters gave voice to their hopes and their values, voted for change, and refused to be invisible any longer," she said.
Senator Obama becomes one of America's youngest presidents behind big names including Theodore Roosevelt and John F. Kennedy.
He paid homage to his grandmother Madelyn Dunham, who died earlier this week from cancer.
"While she's no longer with us, I know my grandmother is watching, along with the family that made me who I am. I miss them tonight, and know that my debt to them is beyond measure," he said.
Scenes of joy also erupted in the US capital and across the country as crowds poured on to the streets, honking horns, dancing and singing.
A delirious crowd of about 2000 gathered around the White House chanting Senator Obama's name.
"La-la-la, la-la-la, hey-hey-hey – goodbye," they sang as President Bush watched events unfold on TV inside.
Among the throng was Ted Howard, a 64-year-old African-American who finally saw slain civil rights leader Martin Luther King's 45-year-old dream of racial equality come to pass.
"I never thought I'd see a day like this," said Mr Howard, who cast his first vote for president for John F. Kennedy in 1960 and witnessed the funeral procession of that leader after he was slain in 1963.
"It's more spiritual than political," he said.
"I am extremely emotional. Everybody's hugging each other. There's love in the air."
- news.com.au - Stefanie Balogh in Chicago