Americans are set to vote in one of the most divisive presidential elections in decades, pitting incumbent Republican Donald Trump against his Democratic challenger Joe Biden.
The first polls will open from 05:00 EDT (10:00 GMT) in Vermont.
Nearly 100 million people have already cast their ballots in early voting, putting the country on course for its highest turnout in a century.
Both rivals spent the final hours of the race rallying in key swing states.
National polls give a firm lead to Mr Biden, but it is a closer race in the states that could decide the outcome.
In the US election, voters decide state-level contests rather than an overall single national one.
To be elected president, a candidate must win at least 270 votes in what is called the electoral college. Each US state gets a certain number of votes partly based on its population and there are a total of 538 up for grabs.
This system explains why it is possible for a candidate to win the most votes nationally – like Hillary Clinton did in 2016 – but still lose the election.
Tuesday’s vote comes amid the ongoing coronavirus pandemic. The US has recorded more cases and more deaths than any other country worldwide, reporting more than 84,000 new infections on Monday alone.
As the nation counts down the hours to the vote, there are fears that pockets of post-election violence could break out. Businesses in the nation’s capital, Washington DC, and in New York City have been seen boarding up their premises due to concerns about unrest.