65 ILCS 5/3.1-35-30
The mayor or president may designate in writing another person to affix the signature of the mayor or president to any written instrument or instruments required to be signed by the mayor or president. The mayor or president shall send written notice of this designation to the corporate authorities, stating the name of the person who has been selected and what instrument or instruments the person will have authority to sign. A written signature of the mayor or president executed by the designated person, with the signature of the designated person underneath, shall be attached to the notice. The notice, with the signatures attached, shall be recorded in the journal of the corporate authorities and then filed with the municipal clerk. When the signature of the mayor or president is placed on a written instrument at the direction of the mayor or president in the specified manner, the instrument or instruments, in all respects, shall be as binding on the municipality as if signed by the mayor or president in person.
65 ILCS 5/3.1-35-30