More than 84.5 million Americans have already cast their votes for the election, according to data from the United States Elections Project.
According to the group, more than 25m of those votes were cast in the three most populous US states - California, Texas and Florida.
More Democrats have voted so far than Republicans, it says.
In Texas, more than 9m people have voted so far, surpassing the total number of votes there in the 2016 election, according to the Associated Press.
Early voting can be by done by post or in-person at a polling station.
Some experts are predicting this election will see the highest turnout since 1908.