49 CFR 372.233: Chicago, IL.

The zone adjacent to, and commercially a part of Chicago, IL, within which transportation by motor vehicle, in interstate or foreign commerce, not under common control, management, or arrangement for a shipment to or from such zone, is partially exempt from regulation under 49 U.S.C. 13506(b)(1), includes and is comprised of all points as follows:

(a) The municipality of Chicago, IL, itself;

(b) All points within a line drawn 20 miles beyond the municipal limits of Chicago;

(c) All points in Lake County, IL.

(d) All of any municipality any part of which is within the limits of the combined area defined in paragraphs (b) and (c) of this section, and

(e) All of any municipality wholly surrounded, or so surrounded except for a water boundary, by the municipality of Chicago or any other municipality included under the terms of paragraph (d) of this section.