Illinois has traditionally done the plate stays with the owner, not the car for plates, but I think might be switching to California-style plating now, but I do

Illinois has traditionally done the plate stays with the owner, not the car for plates, but I think might be switching to California-style plating now, but I don’t know. They seemed to have relatively random issuance of plate numbers but have the constraint that letters cannot follow digits even on vanity plates (so EL1TE would not be a valid plate).¹ Sometime around 2016ish they started issuing plates sequentially with a scheme of AA 12345 but they had previously issued some plates that were AA1 2345 so presumably they need to skip the conflicting plates that followed that scheme. They’ve never had the kind of clear system that California has where standard plate numbers followed a predictable pattern. ⸻ 1. They do, however for specialty plates, have plates which have two letters at the end, usually stacked vertically on the right side of the plate, so, e.g., a stacked SD for people with the duck environmental plate.