Barack Obama, who was chosen to become the 44th president of the US Tuesday, told cheering supporters "change has come to America" and called on Americans to unite to tackle the country's pressing challenges.
Barack Obama: The next president of the United States
In a powerful speech in front of a crowd of an estimated 100,000 people jammed into Chicago's Grant Park on Tuesday, US President-elect Obama said a new dawn of American leadership was at hand and stressed the shared destiny of the United States and the rest of the world.
"It's been a long time coming. But tonight, because of what we did on this day, in this election, at this defining moment, change has come to America," Obama said.
Chicago's Grant Park was a sea of cheering Barack Obama supporters
"All of those watching tonight from beyond our shores, in the parliament and in the palaces, those huddled around radios in the forgotten corners of the world, our stories are singular but our destiny is shared," Obama said.
"A new dawn of American leadership is at hand," he added to roars of applause. "To those who would tear the world down, we will defeat you. To those who seek peace and security, we support you."
McCain says Americans "have spoken clearly"
Obama, 47, won a historic US presidential election after gaining more than 300 electoral college votes, making him the first African-American ever to lead the United States.
He had a commanding victory over Republican rival John McCain, 72, capturing a series of normally reliable Republican states including Virginia and Ohio that voted for President George W. Bush in the last two elections.
McCain with wife Cindy during his speech conceding defeat
Earlier, McCain conceded the presidential race to Barack Obama, saying the Democrat has achieved a "great thing" for himself and the country with his historic victory.
Flanked by wife Cindy and running-mate Sarah Palin, McCain spoke to supporters outside the Arizona Biltmore Hotel, saying the "American people have spoken and they have spoken clearly."
McCain urged his supporters to put aside partisan differences and work to get "the country moving again."
McCain stressed the historic nature of the election, noting that an invitation to black author Booker T. Washington to dine at the White House by Theodore Roosevelt had been viewed as an insult in some quarters.
McCain conceded the contest as polls closed on the West Coast, adding a string of states to Obama's electoral vote tally and sealing the Illinois senator's victory.
Obama had already taken a commanding lead in the US presidential election before the official projection, capturing the key swing states of Pennsylvania and Ohio earlier in the night and leaving McCain with an almost impossible uphill battle to keep his hopes alive.
Ohio nail in McCain campaign's coffin
No candidate has captured the White House without Ohio's 20 electoral votes since 1960. No Republican has ever won the presidency without it. Similarly in Virginia, no Democrat has won the state since 1964.
Obama supporters in Phoenix Arizona erupt in joy
Pennsylvania, with 21 electoral votes, had been considered McCain's best shot of capturing a reliable Democratic state. McCain did not win a single state taken by Democrat John Kerry four years ago.
A total of 270 electoral votes is needed to win in the country's state-by-state, winner-takes-all US electoral system.
Some of the other key states captured by Obama included Michigan, Wisconsin, New Hampshire, New Mexico and Iowa. Georgia, South Carolina, Louisiana and Texas were some of the largest taken by McCain.
Economy topped voters' concerns
Millions of voters had waited for hours at polling stations across the country as McCain and Obama made a final push for votes in swing states.
Democrats worked on the hope that eight years of President George W. Bush's unpopular policies in Iraq and the slumping economy would convince voters to hand them control of the White House and strengthen their control of Congress.
The faltering US economy was by far the top concern of voters heading to the polls in Tuesday's general election, according to initial exit polls reported by US broadcaster CNN.
Millions of voters turned out to vote early
A full 62 percent of voters ranked the economy as the key issue of this election, compared to 10 percent invoking the war in Iraq and 9 percent rating terrorism or health care highest.
Millions already voted in recent weeks in early or absentee voting allowed in 31 states, including key battlegrounds Florida, North Carolina, Colorado and Nevada.
Voters waited patiently in serpentine queues early Tuesday to cast ballots. Many had started lining up before dawn, and some braved pouring rain to cast their ballots.
It was a bittersweet end to the 21-month campaign for Obama, whose grandmother, Madelyn Dunham, 86, passed away overnight Sunday after a battle with cancer, the Illinois senator revealed Monday.