Americans are heading to the polls to choose a new president after one of the most rancorous election campaigns the country has seen.
Voting gets under way in earnest on the East Coast from 06:00 EST (11:00 GMT), though some villages in New Hampshire have already polled.
Hillary Clinton and Donald Trump criss-crossed America in a hectic last-minute campaign push for votes.
Results should begin emerging late on Tuesday night, US time, from 04:00 GMT.
Both candidates have held rallies in the battleground states of North Carolina, Pennsylvania and Michigan.
Mrs Clinton urged voters to back a “hopeful, inclusive, big-hearted America” while Mr Trump told supporters they had a “magnificent chance to beat the corrupt system”.
Polls give Democrat Mrs Clinton a four-point lead over Republican Mr Trump.
A record number of Americans – more than 46 million – have voted early by post or at polling stations.
There are signs of a high turnout among Hispanic voters, which is believed to favour Mrs Clinton.
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The rivals held the final rallies of their campaigns after midnight – Mr Trump in Grand Rapids, Michigan, and Mrs Clinton in Raleigh, North Carolina.
“Today the American working class is going to strike back, finally,” said Mr Trump, pledging to reverse job losses.
Earlier, in New Hampshire, he told supporters: “We are just one day away from the change you’ve been waiting for all your life.
“Together we will make America wealthy again, we will make America strong again, we will make America safe again and we will make America great again.”
Mrs Clinton told her audience that they did not “have to accept a dark and divisive vision of America”.
She looked forward to “a fairer, stronger, better America. An America where we build bridges, not walls. And where we prove conclusively that love trumps hate”.
Akin is the author of the book "THE INTERNET: a town square for the global village.