The prospect of choosing between two presidential candidates with Illinois connections helped draw people to the polls in record numbers.
American University's Center for the Study of the American Electorate says nearly 33 percent of Illinois' eligible voters cast votes in yesterday's primary election. The previous record was 29.7 percent in 1980.
Local election officials around the state confirmed heavy turnout.
Cook County reported a new record. Fifty-two percent of registered voters cast votes, compared to 40 percent in 1992 and 44 percent in 1952.
Several places also saw surges in voters, including the city of Chicago, and Sangamon and Champaign counties.
Democrat Barack Obama lives in Chicago, and former first lady Hillary Clinton grew up in Park Ridge.