Before you marry in Illinois, you must obtain a marriage license from the Recorder of Deeds office in an Illinois county. Both bride and groom must appear at the same time. Both will need to provide picture identification and age. If there are previous marriages, the date(s) that the last marriage(s) ended must be provided, and a period of 30 days must pass before applying for a marriage license.
If you are 16 or 17 years of age, you will have to provide a copy of your birth certificate along with some other sort of identification showing your date of birth. You will also need to have the sworn consent from each parent, each legal guardian or a judge - in person - before the county clerk at the time of application. Your parents or guardians will need to provide identification like a driver's license, state identification card, Illinois Department of Public Aid card, or passport. If your parent is deceased, you will need to show a death certificate or proof of guardianship, or a court order waiving consent. A legal guardian will also need to show a certified copy of the guardianship papers. If you are under sixteen (16) years of age, you cannot get married in Illinois.
Illinois marriage licenses are valid for sixty (60) days only in the county in which it was issued.
Here are some links for local counties: