605 ILCS 5/2-102

The county highway system includes the following highways:

(a) Highways which were State aid roads under the provisions of "An Act to revise the law in relation to roads and bridges", approved June 27, 1913, as amended, immediately prior to the effective date of this Code together with municipal extensions thereof constructed prior to such effective date and for which the county was responsible for maintenance, in whole or in part, under the provisions of Section 32 of that Act, Section 12 of "An Act in relation to State highways", approved June 24, 1921, as amended, or Section 9 of the "Motor Fuel Tax Law", approved March 25, 1929, as amended.

(b) Highways selected and improved as federal aid secondary highways under the provisions of Section 11a of "An Act in relation to State highways", approved June 24, 1921, as amended, which a county has agreed to maintain pursuant to an agreement between the Department and a county under the provisions of that Act.

(c) Highways on which construction is completed after the effective date of this Code and which under the provisions of this Code become a part of the county highway system.

(d) Highways added to the county highway system under the provisions of this Code.

(e) Any access road constructed under Section 10-22.36A of The School Code and connecting school grounds with any highway described in the preceding paragraphs of this Section.