It doesn't matter where you live... it is "where you are standing" during the ceremony. You must be together - there is NO proxi in Illinois. There is a one day waiting period after you obtain a marriage license, unles you're military. Buy your marriage license in the county you want the ceremony to be performed in. See below.
RULE 1: You must have a license from the county where the ceremony will take place.
RULE 2: you can not get married the same day you buy your license, Unless you're active military, see below.
RULE 3: You must both be together when you buy your license. Some states offer Proxy Illinois is NOT one of them.
Rule 4: You must be 18 years of age or older and pay the marriage license fee of $60+ check the website.
FYI: DID YOU KNOW?
YES> You can apply online for the marriage license but still must go together to pick it up
NO> You do not have to show proof of divorce if it has been over 2 years
NO> Blood Test is Required
YES> 1ST Cousin Marriage is Legal if your 50 years old
YES> Active Military Can Marry the Same Day Requires a free stamp on license
YES> if you are age 16 and 17 years old you get married with parental consent
NO> You do not have to change your name. But if you choose to - one, or "both" of you could change your last names. First names are much harder, but possible.