As of 2014, Illinois has 20 votes in the United States Electoral College. This is based on the census of 2010 and represents a decrease of 1 vote from the previous census. Illinois was confirmed to have 20 votes for the 2016 and 2020 elections based on this census.
The Electoral College was established in the Constitution by the founding fathers. It is meant to be a compromise between having a popular vote and a Congressional vote. Each state has a number of electors based on the state's population, which equals the number of Congressional delegates. The votes for Illinois equal the two senators and 18 representatives in the House of Representatives.
In a presidential election, each candidate has a set of electors. Those electors vote for a candidate if that person wins the vote from the state. The total number of electors in the United States is 538. A candidate needs 270 to win the presidency.