Iowa is a perfectly ordinary Midwestern state famous for corn and the University of Iowa Hawkeyes football team. With three million people, the population of Iowa doesn’t even match that of the entire city of Los Angeles. In fact, Iowa only makes up about 1% of the entire population of the United States. Yet every four years, Iowa becomes center stage when it hosts the very first voting event that helps determine the presidential candidates that election year. The Iowa caucus is the election kickoff, and the results are often a good indicator of who will end up running for president of the United States.

What is a caucus? It’s a party meeting of the members of a state’s legislative body in order to select candidates or decide policy. Once the most common way for a state to choose presidential nominees, today only a handful of states rely on the caucus as their only means of determining candidates. Other states participate in primaries or a combination of voting practices to determine their candidates.

What is the major difference between a primary and a caucus? During a primary, voters cast secret ballots while caucuses allow open shows of support for candidates. Back in 1972, Iowa sort of fell into the position of being the first state of hold either a caucus or a primary. It used to be that party bosses could schedule primaries or caucuses at any time without informing anyone. In 1972, the Democratic rules were changed so that a 30-day notice was required. Through a series of scheduling conflicts and moving events to earlier in the year in order to follow the 20-day requirement, the Iowan Democratic party ended up holding their caucus in January, just in front of the New Hampshire primary.

In 1976, a relatively unknown Jimmy Carter noted that Iowa was the first major voting event, so he spent a considerable amount of time campaigning in the state. Though he didn’t win Iowa, he made an impressive showing, getting him noticed by his party members across the country. Ultimately, he won the presidency.

The Republican and Democratic parties in Iowa agreed to hold their caucuses on the same date, securing the state’s enviable status as first-in-line come voting season. In order to maintain a semblance of order and to avoid “frontloading,” the national parties now penalize states that try and hold their voting events early. Because Iowa goes first, it gets ample media attention, which in turn draws candidates to the small Midwestern state.

This year was no different. Hillary Clinton and Bernie Sanders both wooed Democratic voters while Trump, Cruz, Rubio, Christie, Bush, and Carson hoped to do well among Republican voters. The results? Martin O’Malley, a third democratic candidate, dropped out of the race completely after gaining very few votes. Clinton won the caucus, but just by a hair. Bernie Sanders’ strong support in Iowa showed that he is a top contender for the democratic nomination, and his success in Iowa helped fuel his strong win in the New Hampshire primary.

On the Republican side, Donald Trump’s team was shocked when he lost to Ted Cruz. An equally big surprise was how young Florida senator Marco Rubio garnered nearly as many votes as Trump, bolstering his confidence and therefore his campaign. After the Iowa caucus, libertarian-minded Rand Paul dropped out of the race completely.

The results of the Iowa caucus don’t determine who will win the nomination, but they do often determine which candidates will move forward, and which will probably start dropping out of the race soon. In fact, in the New Hampshire primary Donald Trump defeated Ted Cruz while Sanders trounced Clinton. Meanwhile, Chris Christie and Carly Fiorina ended their presidential bids. As the primaries and caucuses continue, the candidate list thins out considerably until just one from each party remains. After that? The presidential race really starts to heat up.

So far, the fight for the nomination has been unpredictable. Were you surprised by the results in Iowa? Who do you think will win the Republican and Democratic nominations?