The US has two main political parties - the Republicans and the Democrats.
Every president since 1853 has belonged to one of these two political parties.
They both have different ideas about how the country should be run, and they also have different animals that represent them.
The Republican party is represented by an elephant and the Democratic party is recognised by the symbol of a donkey.
But why is this?
Well, it is thought the Republican elephant was first used like this by an Illinois newspaper during Abraham Lincoln's 1860 election campaign - perhaps as a symbol of strength, although it is still debated.
It was then made popular after a man called Thomas Nast - who was a Republican - drew it in a cartoon in a magazine in 1874.
As for the Democratic donkey, it is thought this was first used during a presidential campaign in 1828, after the candidate Andrew Jackson used it on his posters because of a nickname his opponents gave him.
Again, Thomas Nast later used the cartoon animal to represent the Democrats and it became a popular symbol for the party by the end of the 19th century.