Today, America will finally find out who will lead it for the next five years.
For those planning to stay up and watch the results roll in tonight, here is what you need to know.
By the day’s end, more than 130 million Americans out of an eligible 225 million are expected to have cast ballots across the 50 states. But the voting system is nothing like the UK’s.
Instead, the election is determined by the mysterious Electoral College – a group of people known as “electors”, appointed by each party. Their total number is equal to the number of members in Congress – 535 – plus three electors from the District of Columbia. But the number in each state varies, depending on the size of its population.
As the largest state, California has 55 electoral college votes, while sparsely populated Wyoming and tiny Washington DC have only three each. So if Hillary Clinton were to win Wyoming, she will get all three electoral votes. The goal is to get to 270, which is just over half of 538.
All but two states – Maine and Nebraska – use a winner-takes-all system. So if you win the most votes in a state, you take all of its electoral college votes.
The drama is likely to unfold in swing states such as Arizona, Colorado, Ohio and Florida, where the election has been hardest fought.
The first polls close at about 11pm GMT in Kentucky and Indiana, home to Mr Trump’s running-mate Mike Pence. Voting in the crucial battlegrounds of Florida and Ohio closes soon after midnight.
Look out for Florida in particular: a Clinton win there would probably spell curtains for Mr Trump. If you are willing to believe the exit polls, you might even have a (relatively) early night.
Ms Clinton starts with an advantage in the Electoral College and she could afford to lose Ohio and Florida, but if she were to fall short in North Carolina and Pennsylvania, Mr Trump would probably succeed.
Safe Republican and Democratic states will probably declare their results early, but it could be well into tomorrow morning by the time the results become clear in swing states.
One thing to watch out for is voter turnout, particularly among Hispanic voters in places like Arizona, Florida and Nevada, and African-American voters in states like Ohio and North Carolina. If their numbers are low, it could pose trouble for Ms Clinton.
After Barack Obama won the past two elections comfortably, John McCain and Mitt Romney gave concession speeches at about 5am. But if neither Mr Trump nor Ms Clinton reaches the 270 mark, the Republican-controlled House of Representatives will decide the outcome – and we could end up with President Trump after all.