User:Hawkeygoal/IL Pages/IL Highway Numbering (2016 06) History


The goal of this page update is to revise the US, State, and County Route Naming portion of the Major roads section of the Illinois wiki.

This information is under consideration for the Illinois state wiki.
It should not be considered official guidance.

Illinois counties maintain a system of routes or highways within their borders. A separate coordinate-based system for rural county roads also maintained. At present, both are prefixed "CR-." The principal change in this update is to alter that guidance.

The current wiki guidance on this topic can be found in this section.


Road naming

In Illinois, USA road naming guidance is followed with the following local exceptions:

  • State Routes or Highways are named with SR-XXX.
  • County Routes or Highways are named CH-XXX.
  • County Roads are named CR-XXX.
  • Township Roads are named TR-XXX.

Numbering and direction follow USA road naming guidance. When county highways contain a letter, the format is CH-XNN. For example, CH-W25.

County Highways (CH) typically carry a locally designated primary name used for addressing. CH have 1-3 a alphanumeric character designation (e.g. CH-7 and CH-A19) usually listed as alternate name. CH may be assigned a higher road type classification (FC Quick Reference Chart).

When used, County Roads (CR) are coordinate-based, 3-4 digits with a cardinal direction (e.g. CR-2300 E or CR-600 N). They are used for addressing. CR designations are generally primary names for this reason, but may be listed as alternate. There is no special consideration for CR in functional classification and road types.

Proper sourcing of county routes and highways is important. CH may or may not always be shielded. Sources other than WME SV may need to be used. The interactive IDOT functional classification map uses a third-party base map source which is subject to copyright restrictions and may not be correct, therefore, it should not be used as a source for naming information. In order of preference, source county route/highway numbering from WME SV images less than three years old (consult LAM or SM if images are older), published county information, or the IDOT county highway maps available at IDOT Maps.

The naming guidance for county highways was changed in July 2016. Previously, county highways were also labeled "CR-" and should be updated to the new guidance when on a segment. Care must be taken to not change the naming of county/township roads which are currently named using "CR-." See the state to-do list for counties outstanding.

Additional Changes

This will require additional updates to the USA Highway naming page to reflect amended guidance.

Need to update Functional Classification page with usage of interactive map.


This proposal is under discussion on the forums, at the following link: