The county is suing the two outlying towns, claiming their tax-incentive programs rob local governments of tax proceeds.
Chicago and the Regional Transportation Authority have already filed lawsuits against the towns, which have programs encouraging businesses to come to their communities and avoid higher sales taxes.
The communities then share a portion of the sales tax with the companies. Cook County Board President Toni Preckwinkle calls it a wrongful kickback scheme.
"Every retail sale that is wrongly sourced to Kankakee and Channahon hurts law-abiding businesses and robs other local governments, like Cook County," Preckwinkle said.
Officials in Channahon and Kankakee say they're following the law and bringing jobs to Illinois.