Chapter 7. While the Polls Are Open, this link opens in a new browser tab.

The judges in charge of the precinct registration files shall compare the signature upon such certificate with the signature on the registration record card as a means of identifying the voter.

Unless satisfied by such comparison that the applicant to vote is the identical person who is registered under the same name, the judges shall ask such applicant the questions for identification which appear on the registration card, and if the applicant does not prove to the satisfaction of a majority of the judges of the election precinct that he is the identical person registered under the name in question then the vote of such applicant shall be challenged by a judge of election, and the same procedure followed as provided by law for challenged voters.

In case the elector is unable to sign his name, a judge of election shall check the data on the registration card and shall check the address given, with the registered address, in order to determine whether he is entitled to vote.

10 ILCS 5/4-22, this link opens in a new browser tab.
Counties Having a
Population of Fewer Than 500,000

10 ILCS 5/5-29, this link opens in a new browser tab.
Counties Having a
Population of 500,000 or More

10 ILCS 5/6-66, this link opens in a new browser tab.
Jurisdictions With
Local Boards of Election Commissioners

Pollwatchers shall be permitted... to station themselves in a position in the voting room as will enable them to observe the judges making the signature comparison between the voter application and the voter registration record card; provided, however, that such pollwatchers shall not be permitted to station themselves in such close proximity to the judges of election so as to interfere with the orderly conduct of the election...

10 ILCS 5/7-34, this link opens in a new browser tab.
Primaries.

10 ILCS 5/17-23, this link opens in a new browser tab.
General, municipal, special,
and consolidated elections.