Mice and rats are opportunists, and Glen Ellyn properties give them plenty of opportunity. Historic brick two- and three-flat buildings make up much of the older city housing stock, alongside postwar suburban tract homes. Once inside a wall void or attic space, they're difficult to remove without sealing the entry point that let them in.
Exclusion is the core of effective rodent control: finding and sealing every gap a mouse or rat could use to get inside, since traps alone just remove the current population without stopping the next one. We pair exterior sealing with interior trapping or bait stations, then follow up to confirm the problem is resolved.