Kim Foxx is the Democratic incumbent.
WATCH: NEWSVIEWS PART 1
Cook County state's attorney candidates Kim Foxx, Pat O'Brien, Brian Dennehy discuss issues
She is the first African American woman to hold the job.
Foxx said she's running for a second term because she wants to "continue the important work of reforming justice and making a fairer, safer system for Cook County."
The Republican candidate is Judge Pat O'Brien.
WATCH: NEWSVIEWS PART 2
Cook County state's attorney candidates Kim Foxx, Pat O'Brien, Brian Dennehy discuss issues
He spent nine years as a Cook County judge. And O'Brien has previously worked in the state's attorney's office.
He later served as an assistant Illinois attorney general.
O'Brien said the state's attorney's office needs to change, and he is the person to "restore integrity and order."
The third candidate is Libertarian Brian Dennehy.
WATCH: NEWSVIEWS PART 3
Cook County state's attorney candidates Kim Foxx, Pat O'Brien, Brian Dennehy discuss issues
He's an attorney and accountant who has described his political background as "upset citizen."
Dennehy has said, if elected, his focus would be on those who harm other people.