Iowa caucuses

The Iowa Caucus is an electoral event in which residents of the U.S. state of Iowa meet in precinct caucuses in all of Iowa's 1,681 precincts and elect delegates to the corresponding conventions in each of the state's 99 counties. These county conventions then select delegates for both Iowa's Congressional District Convention and the State Convention, which eventually choose the delegates for the presidential nominating conventions. About 1% of the nation's delegates are chosen by the Iowa State Convention. The Iowa Caucus is noteworthy for the amount of media attention it receives during U.S. presidential election years. Since 1972, the Iowa caucuses have been the first major electoral event of the nominating process for President of the United States. Since 1972, the Iowa caucuses have had a 43% success rate at predicting which Democratic candidate for president and a 50% success rate at predicting which Republican candidate for president will go on to win the nomination of their political party at that party's national convention, though they may more reliably indicate which ones are likely to drop out owing to lack of support.

In 2016, the Iowa Democratic and Republican Party precinct caucuses took place on Monday, February 1 with one hour of voting beginning at 7:00pm Central Standard Time. For the first time, results were electronically sent to both Democratic and Republican headquarters.

After the 1968 Democratic National Convention protest activity, the Democratic Party decided to make changes to their presidential nominating process by spreading out the schedule in each state. Since Iowa had a complex process of precinct caucuses, county conventions, district conventions, and a state convention, they chose to start early. In 1972, Iowa was the first state to hold their Democratic caucus, and had the first Republican caucus four years later.

...
Wikipedia