District Map (source, DuPage County GIS, 2019)
The District boundaries for CUSD 201 are described in the following image (click the image to download the full size version - 24 MB).
DuPage County Parcel Viewer: https://gis.dupageco.org/parcelviewer/
Look up addresses by address or parcel number. Click inside the parcel and a pop-up with "Property Districts" (scroll down if necessary) will list if UnitSchoolDist is "District 201" confirming the property is inside CUSD 201 borders.
DuPage County Unit School Districts: https://dupage.maps.arcgis.com/home/webmap/viewer.html?webmap=709585bb38734964afd0afb8ef443ff3
Look up addresses to confirm if within CUSD 201 (District 201) boundaries.