Margarita Hernandez is charged with aggravated criminal sexual abuse.
Joliet Police Chief Mike Trafton said the arrest is related to an ongoing federal investigation of child pornography. Hernandez is a Democratic committeewoman in Troy Township in Will County.
The incident allegedly happened July 10. Relatives of the 15-year-old victim later contacted police.
Hernandez is being held on $200,000 dollars bond.