605 ILCS 5/5-102

Upon the effective date of this Code the highways comprising the county highway system in each county are those highways that, on such date, are defined as county highways by Section 2-102 and 2-204 of this Code.

Additions to and deletions from the county highway system may be made in the manner prescribed in this Code. Highways added to the county highway system shall be as nearly as possible highways connecting the principal municipalities and trading points in each county with each other, and also with the principal municipalities and trading points in other counties.