Unincorporated addresses in Kane and DuPage Counties do use a reference system based off State & Madison as baseline (although it's been codified based off county and township lines). Eg. 40W100 Keslinger Rd is a bit over 40 miles west of State St.
They have their own section in the postal addressing standards, under the "Unusual Addressing Situations":
I spent 20+ years in Washington, DC so am used to NW, NE, SW, and SE with avenues, numbered streets, flower streets of two syllables, blah blah blah. But I now live in rural Virginia and state routes are the norm.
Your explanation got me to focus more on what and why. And, I learned something, so thank you.