With an anxious world watching, Americans began voting Tuesday on whether to send the first female president or a volatile populist tycoon to the White House.
The kickoff marks the end to a campaign like no other- exhausting, often bitter- as Hillary Clinton and Donald Trump presented radically different visions of how to lead the world’s greatest power.
Polls opened at 6:00 am (1100 GMT) in nine states, mainly in the east. The name of the winner was not expected to be known before 0300 GMT.
Clinton has a slim lead in the polls but no one was ruling out a Trump win.
Democratic frontrunner Clinton and Republican maverick Trump campaigned into the early hours of Election Day, capping a grueling final day of wooing voters.
The 69-year-old former first lady, senator and secretary of state- backed by A-list musical stars and incumbent President Barack Obama- urged the country to unite and vote for “a hopeful, inclusive, big-hearted America.”
Trump meanwhile pressed his message with voters who feel left behind by globalization and social change, wrapping up with a flourish on his protectionist slogan: “America first.”
“Just imagine what our country could accomplish if we started working together as one people, under one God, saluting one American flag,” the 70-year-old billionaire reality television star told cheering supporters.
Some 40 million Americans have already cast ballots in states that allow early voting, and opinion polls suggest Clinton has a slight edge.
In their kick-off midnight vote, the residents of tiny Dixville Notch in New Hampshire cast their traditional first-in-nation ballots with a total of eight votes- Clinton getting four and Trump, two.
The others went to a fringe candidate and Mitt Romney, the failed Republican hopeful in 2012.
A polling average by tracker site RealClearPolitics gave Clinton a 3.3-percentage point national lead, but Trump is closer or even has the advantage in several of the swing states that he must conquer to pull off an upset.
No results or exit polls will be available before polling stations begin to close on the US East Coast from 7:00 pm (0000 GMT Wednesday), and it may be three or more hours after that before the direction of the race becomes clear.
And even then, questions remain. Trump has repeatedly warned that a “corrupt Washington and media elite” is seeking to rig the race and he said last month that he may not concede defeat if he thinks voting is unfair.
He has also threatened to lodge lawsuits against up to a dozen women who have come forward during the race to accuse him of sexual assault or inappropriate behavior.