While some states are well and truly tied up by the Republican or Democratic parties, others could go either way.
A swing state is one where the two major parties have similar levels of support amongst voters. This tight nature of voting in these states means they are usually a good indicator of who will win the election overall.
How important swing states are depends on their size and a system known as the electoral college - the short video below explains this process.
As you can see, the US election process is complicated b- ut the short answer of it is electoral votes mean everything, and the golden number of them needed to win the presidency is 270. This means swing states, particularly large ones, are pivotal.
Defining such states can vary depending on which polls you read and, as we learned from Britain's EU referendum, polls can be counted on being unreliable. However, here are the swing states you should almost certainly keep an eye out for.
Florida - 29 electoral votes
Florida is famous for its beaches due to its hundreds of miles of coastline and its epic theme parks such as Disney World, pictured above. With 29 electoral votes and a winner-takes-all policy, Florida is also a famously pivotal state in US elections. Florida has voted for the presidential winner for every year except one since 1960.
This election, Florida looks as close as you can get - with the latest polls indicating a dead heat between Clinton and Trump.
The results from Florida will come in at 1am UK time (8pm EST) and with many states looking easy seats for Clinton, it is a must win for Trump - so be on the lookout.
Ohio - 18 electoral votes
Ohio is famous for producing famous people, producing seven Presidents, 24 astronauts and other public figures such as director Steven Spielberg and historic inventor Thomas Edison. Like Florida, Ohio always seems to choose the winner of the election - having not voted against them since 1964.
Polls show Trump has done well in Ohio so far, with a two-point lead opening up against Clinton - but expect the unexpected results for Ohio come in at 12:30am GMT.
Georgia - 16 electoral votes
Georgia is a state magnificent at farming, with rural communities acting as some of the USA's top producers of peanuts, onions and of course peaches.
The polls indicate a relatively strong four-point lead for Trump in this state, but it is likely to go much closer to the wire than in previous years. In the past, a staunchly Republican state, Georgia has a small chance to pull up a pivotal surprise for Clinton.
If you want to see how this state turns out, you'll be looking to get a midnight train to Georgia - so glad this song reference doesn't feel forced - as results will come in from here at about 12am in the UK.
North Carolina - 15 electoral votes
North Carolina is home to the Great Smokey Mountains, a mountain range and US national park. According to some, it is where the Wright brothers flew the first aeroplane at the start of the 20th century - although the people of Ohio also make this claim.
With 15 electors up for grabs, it is another important one and pretty evenly-contested state, with Clinton only two points ahead in recent polls. North Carolina's results come in at 12:30am.
Arizona - 11 electoral votes
Arizona is famous for its desert, with the cactus blossom being its state flower. Despite the desert though, there are more than six-and-a-half million people in Arizona, and its 11 votes could be very important.
Arizona is typically Republican, but a high population of Hispanic people and Trump's detrimental comments towards that demographic means it could act as a swing state. Polls indicate a four-point lead for the business mogul despite this but it will be worth watching - at around 2am UK time.
South Carolina - 9 electoral votes
Other than being the site of the first battle of the American Civil War, at Fort Sumter in 1861, South Carolina doesn't have a huge amount of interesting stuff about it we could find for you to be honest. However, with nearly five million people and nine electors, it's still just as important to the presidential hopefuls.
It looks likely South Carolina will go Trump's way, with a two-point lead in the polls, but Clinton has had a few campaign rallies there, so keep an eye out for it at midnight.
Colorado - 9 electoral votes
Colorado's famous Capitol Building is one of only three sites in the world you can see Beulah Red marble, as the builders used almost all of it from the Beulah Red Marble Quarry to build the building. The mountainous and picturesque state has over five million people too and nine more electors the candidates can fight over.
Clinton has a three-point poll lead at last count, but Trump has been campaigning hard in the area. Who will win it? Find out at 2am.
Iowa - 6 electoral votes
Iowa is another famous for its agriculture, particularly its apparently delicious corn. It's also famous as a true battleground state, changing political allegiance quite regularly over the past 40 years.
Iowa voted for Barack Obama both of the past two elections, but now it looks to be turning red with Trump getting a nod by a massive five points in the polls. This is probably Trump's most likely swing state win so be aware it's coming up at 3am.
Nevada - 6 electoral votes
Nevada is the second largest source of gold in the world and of course is the home to the gambling capital of the world, Las Vegas. As another true battleground state though you best not place a big bet on which way this state will go.
Polls suggest it's too close to call and, released at 3am, Nevada's six votes just might make all the difference if it's looking close.
New Hampshire - 4 electoral votes
New Hampshire is another mountainous state and as it is so far North can have some severe winters. Their state motto is "Live Free or Die", which is emblazoned on license plates across the area.
In the polls, this state looks to be leaning Clinton's way as she has a three-point lead - but should it swing Trump's way at 1am, it could be a big boost for him.
And the rest?
Before you go thinking this list is definitive or anything, be aware that any state can act as a swing state - and depending on who you listen to, there are many more you should be on the look out for. Pennsylvania for example, with 20 electoral votes being announced at 3am, looks likely to go Democrat but some commentators think it could be a close call and a Trump win there could be a gamechanger.
Michigan, Minnesota and Wisconsin also look to be opting for the blue team, but Trump's campaign has targeted to these areas, and with 36 votes in total coming from them - all at 2am - their results could be a huge moment.
Any more questions about timings? Have no fear, our brilliant graphics team is here to help: