Illinois elevation
Illinois runs from 279 ft at Mississippi River to 1,235 ft at Charles Mound, with an average of about 628 ft.
Highest point: Charles Mound
1,235ft
376 m above sea level
Charles Mound, Jo Daviess County · NGVD 29 (the older U.S. vertical datum)
- Lowest point: Mississippi River
- 279 ft (85 m)
- NGVD 29 (the older U.S. vertical datum)
- Source: USGS, Elevations and Distances in the United States (highest and lowest elevations) (revised edition 2001)
- Average elevation (sampled)
- 628 ft (191 m)
- Mean of 221 USGS points about 26 km apart; an estimate, not a published figure.
- Source: USGS 3DEP + 2024 Census boundary
Data updated · By Ankit Kumar, compiled from public U.S. government and open datasets · How these numbers are made
Illinois places on this site
Cities and towns (USGS, downtown)
- Springfield600 ft
Illinois elevation facts
| What | Value | Source |
|---|---|---|
| Highest point: Charles Mound | 1,235 ft (376 m) | USGS, Elevations and Distances in the United States (highest and lowest elevations) (revised edition 2001) |
| Lowest point: Mississippi River | 279 ft (85 m) | USGS, Elevations and Distances in the United States (highest and lowest elevations) (revised edition 2001) |
| Vertical range | 956 ft (291 m) | Difference of the two figures above |
| Average elevation (sampled) | 628 ft (191 m) | USGS 3DEP, 221 grid points |
| USGS 3DEP value at the high point | 1,234 ft (376 m) | USGS 3DEP, within 250 m of the GNIS summit |
| Capital: Springfield | 600 ft (183 m) | USGS 3DEP at the city center |
| Land area | 55,513 sq mi (143,778 km²) | Census 2024 boundary file |
Life at 628 ft
Standard-atmosphere estimates for the state's sampled average elevation (628 ft). Weather moves the real values a little from day to day.
- Oxygen per breath
- 98 % of sea level
- Air is still 20.9% oxygen; there is just less air.
Sources: pressure from the U.S. Standard Atmosphere, 1976 (NOAA, NASA, USAF); boiling point from the Antoine equation for water (Lange's Handbook of Chemistry); canning thresholds from the USDA Complete Guide to Home Canning. Not medical or food-safety advice; follow the tested USDA recipe for your altitude.
City elevations in Illinois
- Rockford717 ft
- Naperville710 ft
- Aurora676 ft
- Springfield (capital)600 ft
- Chicago588 ft
- Joliet541 ft
Largest places in Illinois
The five incorporated places by 2024 Census population estimate.
| What | Value | Source |
|---|---|---|
| Chicago | 588 ft (179 m) · pop. 2,721,308 | USGS 3DEP; Census 2024 estimate |
| Aurora | 676 ft (206 m) · pop. 180,710 | USGS 3DEP; Census 2024 estimate |
| Naperville | 710 ft (216 m) · pop. 153,124 | USGS 3DEP; Census 2024 estimate |
| Joliet | 541 ft (165 m) · pop. 151,837 | USGS 3DEP; Census 2024 estimate |
| Rockford | 717 ft (219 m) · pop. 147,486 | USGS 3DEP; Census 2024 estimate |
Frequently asked questions
What is the highest point in Illinois?
Charles Mound at 1,235 ft (376 m), from USGS, Elevations and Distances in the United States (highest and lowest elevations) (revised edition 2001).
What is the lowest point in Illinois?
Mississippi River, at 279 ft, per the USGS Elevations and Distances table (2001).
What is the average elevation of Illinois?
About 628 ft (191 m): the mean of USGS 3DEP elevations at 221 points on a regular grid about 26 km apart inside the state boundary. It is our estimate, not a published figure.
Which Illinois city on this site is highest?
Springfield, at 600 ft downtown (USGS).
Does altitude affect cooking in Illinois?
At 628 ft, water boils at about 210.9 °F (99.4 °C) and standard air pressure is 29.25 inHg (990 hPa), so each breath holds about 98% of the oxygen it would at sea level. That is for the state's average elevation; check your own town, because Illinois spans 956 ft from lowest to highest.
Sources
- USGS, Elevations and Distances in the United States (highest and lowest elevations) (revised edition 2001) — highest point
- USGS, Elevations and Distances in the United States (highest and lowest elevations) — lowest point
- USGS Elevation Point Query Service (3DEP) — average elevation, city-center values and the high-point check
- U.S. Census Bureau, 2024 Cartographic Boundary Files (places, states; 1:500,000) — state boundary and land area
- U.S. Census Bureau, 2024 Gazetteer Files (places) — city locations
- U.S. Census Bureau, Vintage 2024 Population Estimates (cities and towns, July 1, 2024) — largest cities by population
- Wikidata (elevation statements that cite a source; the cited source is listed with each value) — state capital name
- U.S. Standard Atmosphere, 1976 (NOAA/NASA/USAF); water boiling point by the Antoine equation (Lange’s Handbook of Chemistry) — boiling point, air pressure and oxygen
How each number is produced: methodology and data sources.
Every state: US elevation by state · Highest point in each state
Data updated · By Ankit Kumar, compiled from public U.S. government and open datasets · How these numbers are made