The US's biggest prize battleground state – why it matters
Early results could be released soon in the key swing state of Georgia as polls begin closing in the race to see whether Donald Trump or Kamala Harris will be the next US president.
As expected, Trump has won his home state of Florida and picked up a few other conservative states, while Kamala Harris has taken liberal strongholds such as Vermont, Maryland and Massachusetts, the BBC's US partner, CBS, is projecting.
But there is there is no clear leader so far in the seven swing states that will ultimately decide who wins the White House. Exit polls suggest voters rated the state of democracy and the economy as their most important issues.
Whichever way it goes the result will be historic - either giving America its first woman president or marking a seismic political comeback for Trump.
A high turnout has been predicted, but the outcome may not be known for several days if the results are as close as polls have indicated.
Whoever wins the White House may have their hands tied by Congress, which is also up for grabs in Tuesday’s vote.
Democrats have a slim majority in the Senate, while Republicans narrowly control the House of Representatives.
Republicans took a step towards winning control of the Senate on Tuesday night by wresting a seat in West Virginia from the Democrats.
But neither party seemed to have an advantage in the House.
Polls have closed in Georgia, North Carolina and Pennsylvania - three of the seven swing states expected to determine the outcome. The others are Arizona, Michigan, Nevada and Wisconsin.
Georgia Secretary of State Brad Raffensperger said that by new state law, early votes in the Peach State are required to be publicly reported one hour after polls close.
"You'll get a lot of results really quick," he said.
How swing state voters in Georgia are feeling on election day
Around 86 million voters cast their ballots early amid one of the most turbulent campaigns in recent American history.
Vice-President Harris, 60, only became the Democratic Party candidate in July, after President Joe Biden withdrew from the race under pressure from within the party.
Trump, 78, was the target of two assassination plots - narrowly avoiding a sniper's bullet in Pennsylvania.
The former president said he felt "very confident" as he voted earlier in the day near his home in Palm Beach, Florida, with his wife, Melania.
"If I lose an election, if it's a fair election, I'm going to be the first one to acknowledge it," he said.
He posted earlier on his social media platform, Truth Social, saying "law enforcement coming" to Philadelphia because of "massive cheating".
Philadelphia's police department told BBC Verify they were unaware of any electoral fraud. The city's top prosecutor said the allegation had "no factual basis whatsoever".
Both sides have armies of lawyers on standby for legal challenges on and after election day.
Elon Musk, the world's richest man and Trump mega-donor, is spending election night with the Republican nominee at his Mar-a Lago resort in Florida.
How the US presidential campaign unfolded in 180 seconds
Harris, who voted early by mail in her home state of California, is due later to address students at Howard University, a historically black college in Washington DC, where she was an undergraduate.
"To go back tonight to Howard University, my beloved alma mater, and be able to hopefully recognise this day for what it is is really full circle for me," Harris said on a radio interview earlier.
If she wins, she would become the first woman, black woman and South-Asian American to win the presidency.
Trump would become the first president to win non-consecutive terms in more than 130 years. He is also the only president to be impeached twice and the first former president to be criminally convicted.
Exit polling by CBS suggests that around a third of voters said the state of democracy was their top concern, out of the five options given.
The economy ranked second, with three in 10 voters choosing it, according to the preliminary data.
Abortion and immigration followed on the list, while foreign policy was deemed the least important.
In Detroit, Michigan, one voter, Melissa Klein, told the BBC: "Women's rights are a huge, huge issue for me. I'm a nurse, I work in obstetrics, I'd never want to see a world where we can't help women get the life-saving work they need."
In Las Vegas, Nevada, first-time voter Jasmine Perez, 26, said she had cast her vote for Trump.
"What really attracted me to Donald Trump is I'm a Christian," Ms Perez told AP news agency. "I like that he openly promotes Christianity in America."
Law enforcement agencies nationwide are on high alert for potential violence.
About 30 bomb threats hoaxes targeted election-related locations nationwide on Tuesday, more than half of them in the state of Georgia alone, reports CBS.