The battlegrounds in the Rust Belt of Pennsylvania, Michigan, Wisconsin, and Ohio look as though they could go either way in the White House race. The sunbelt states of Arizona and Texas, once reliably Republican, are also toss-ups. A Biden win in Texas would be a political earthquake.
Nail-biting counts are also underway in two more critical swing states on the East Coast, Georgia, and North Carolina. Both Florida and Pennsylvania are considered must-wins for Mr. Trump if he is to be re-elected to a second term in office.
No surprises have emerged yet in the other states.
It is projected that Mr. Trump will hold on to Alabama, Indiana, North Dakota, South Dakota, Kentucky, Tennessee, Oklahoma, Arkansas, and West Virginia, all as expected.
Joe Biden likely to win in his home state of Delaware, along with New York, Colorado, Vermont, Maryland, Massachusetts, New Jersey, and Washington DC. South Carolina, Nebraska, Kansas, Louisiana, and Wyoming are leaning Mr. Trump’s way. Minnesota, New Mexico, Maine, Connecticut, Illinois, Rhode Island and New Hampshire are trending towards Mr. Biden.
Mr Trump narrowly lost Minnesota in 2016 and his campaign is hoping to pick it up this time.
Voting has ended on the US West Coast at 23:00 EST (04:00 GMT on Wednesday).
Exit poll data suggest Mr Biden had the edge with women voters by 57% to 42%, with black voters (87% to 11%), with under-29 year olds (64% to 33%) and among voters with or without a college degree.
Mr Trump appeared to hold the advantage with over 65 year olds (51% to 48%).