10 ILCS 5/6-27
Every person having resided in the State and in election precinct 30 days next preceding any election therein and who shall be a citizen of the United States of the age of 18 or more years, shall be entitled to vote at such elections described in the last preceding Section.
After the first registration provided by this Article, the vote of no person, other than an elector voting pursuant to Article 20 of this Act or exempt under Section 6-67.01 or 6-67.02 of this Article from registration, shall be received in any election conducted under the provisions of this Article 6 or Articles 14 and 18 of this Act unless such person has registered under the provisions of this Article in the precinct in which such person resides. For the purposes of this Article, the word "election" shall include primary.
No person shall be entitled to be registered in or from any precinct unless such person shall, by the date of the election next following, have resided in the State and within the precinct for 30 days, and be otherwise qualified to vote at such election. Every applicant who shall be 18 years of age on the day of the next election shall be permitted to register, if otherwise qualified.
To constitute residence under this Act, Article 3 is controlling.
10 ILCS 5/6-27