Illinois
URL: https://knowledge.ivjn.us/en/places/illinois/at/3.html

Illinois is a state of the United States with FIPS code 17 and capital Springfield.

## Administrative divisions

Illinois is a state of the United States with FIPS state code 17[^uscb2023]. Below the state level are counties (or independent cities), then municipalities and neighborhoods[^uscb2023].

## Basic facts

- FIPS state code: 17[^uscb2023]
- Capital: Springfield[^enwiki]
- Population: about 12,549,689 (2023 estimate)[^uscb2023]
- Area: 149,995 km2[^enwiki]
- Admitted to the Union: 1818[^enwiki]
- Time zone: Central Time (UTC-6/-5)[^enwiki]
- ISO 3166-2: US-IL[^enwiki]

## Parent division

Located in [United States](https://knowledge.ivjn.us/en/places/united-states.html).

## Subdivisions

Major counties: [Cook County](https://knowledge.ivjn.us/en/places/il-cook-county.html), [DuPage County](https://knowledge.ivjn.us/en/places/il-dupage-county.html), [Lake County](https://knowledge.ivjn.us/en/places/il-lake-county.html), [Will County](https://knowledge.ivjn.us/en/places/il-will-county.html), [Kane County](https://knowledge.ivjn.us/en/places/il-kane-county.html).

Major cities: [Chicago](https://knowledge.ivjn.us/en/places/il-chicago.html), [Aurora](https://knowledge.ivjn.us/en/places/il-aurora.html), [Naperville](https://knowledge.ivjn.us/en/places/il-naperville.html), [Joliet](https://knowledge.ivjn.us/en/places/il-joliet.html).

Updated: 2026-10-29

Relations:
- Located in: United States https://knowledge.ivjn.us/en/places/united-states.html
- Contains places: DuPage County https://knowledge.ivjn.us/en/places/il-dupage-county.html
- Contains places: Cook County https://knowledge.ivjn.us/en/places/il-cook-county.html
- Contains places: Lake County https://knowledge.ivjn.us/en/places/il-lake-county.html
- Contains places: Kane County https://knowledge.ivjn.us/en/places/il-kane-county.html
- Contains places: Will County https://knowledge.ivjn.us/en/places/il-will-county.html
- Contains places: Chicago https://knowledge.ivjn.us/en/places/il-chicago.html
- Contains places: Aurora https://knowledge.ivjn.us/en/places/il-aurora.html
- Contains places: Naperville https://knowledge.ivjn.us/en/places/il-naperville.html
- Contains places: Joliet https://knowledge.ivjn.us/en/places/il-joliet.html
- Contains places: Bond County https://knowledge.ivjn.us/en/places/il-bond-county.html

Sources:
- Illinois (Wikipedia) https://en.wikipedia.org/wiki/Illinois
- U.S. Census Bureau 2023 FIPS state and county codes https://www.census.gov/library/reference/code-lists/ansi.html