Downstate Illinois

Ten Largest Downstate Cities
Rank	City	Population	County
1	Rockford	152,871	Winnebago
2	Springfield	116,250	Sangamon
3	Peoria	115,007	Peoria
4	Champaign	81,055	Champaign
5	Bloomington	76,610	McLean
6	Decatur	76,122	Macon
7	Normal	52,497	McLean
8	Moline	45,883	Rock Island
9	Belleville	44,478	St. Clair
10	Urbana	41,250	Champaign

Downstate Illinois refers to all of Illinois south of the Chicago metropolitan area. This term is flexible, but because it is generally meant to refer to everything outside the Chicago area; some cities in Northern Illinois, such as Rockford (which is north of Chicago), are also considered to be "downstate". Prior to the issuance of 2000 Census results, when it became part of the Chicago metropolitan area, even DeKalb (located 65 miles west of Chicago) was often considered to be "downstate".

The term has been part of the Illinois lexis for decades, and is commonly used by the media. The General Assembly (the state legislature for Illinois) regularly makes references to the term in the titles of bills it passes.

Most of the state's largest cities (six of the top ten) are concentrated in and around the Chicago area, but several mid-sized cities exist in the downstate area as well.

...
Wikipedia