Illinois spans 57,914 square miles and features diverse landscapes, including the fertile Central Plains, the rugged Driftless Area in the northwest, and the elevated Shawnee Hills in the south, home to Charles Mound, the state’s highest point at 1,235 feet. Major water bodies include the Mississippi River on the western border, the Ohio River in the southeast, and Lake Michigan to the northeast. This geographic diversity supports agriculture, industry, and a range of ecosystems, making Illinois a vital hub in the Midwest.
Explore physical map of Illinois state of United States showing geographical / physical features with rivers, landforms, mountains, plateau, peaks, lakes, etc.
Geographical Facts of Illinois
Fact
Detail
Total Area
57,914 square miles
Land Area
55,593 square miles
Water Area
2,320 square miles
Highest Point
Charles Mound, 1,235 feet above sea level
Lowest Point
Confluence of Mississippi and Ohio Rivers, 279 feet above sea level
Major Rivers
Mississippi River, Illinois River, Ohio River, Wabash River
Major Lakes
Lake Michigan, Carlyle Lake, Rend Lake
Bordering States
Wisconsin, Iowa, Missouri, Kentucky, Indiana
Climate
Humid continental, with hot summers and cold winters
Average Annual Precipitation
35 inches in the north to 48 inches in the south
State Tree
White Oak
State Flower
Violet
State Nickname
The Prairie State
Population (2023 Estimate)
12.8 million
Largest City
Chicago
Capital City
Springfield
Regions
Northern Illinois, Central Illinois, Southern Illinois
Time Zone
Central Standard Time (CST)
Famous Landforms
Shawnee Hills, Mississippi River bluffs, Driftless Area
Notable Scenic Byways
Great River Road, Illinois River Road National Scenic Byway
Rivers of Illinois
River Name
Length (Miles)
Source
Mouth
Major Tributaries
Notable Features
Mississippi River
2,320 (580 miles along Illinois)
Lake Itasca, Minnesota
Gulf of Mexico
Illinois River, Missouri River, Ohio River
Forms Illinois's western border; vital for commerce and wildlife
Illinois River
273
Confluence of Kankakee and Des Plaines Rivers
Mississippi River
Fox River, Vermilion River
Major transportation waterway; supports ecosystems and recreation
Ohio River
981 (133 miles along Illinois)
Confluence of Allegheny and Monongahela Rivers
Mississippi River
Tennessee River, Wabash River
Forms Illinois's southeastern border; crucial for navigation
Wabash River
503
Fort Recovery, Ohio
Ohio River
Little Wabash River, Embarras River
Forms part of Illinois's eastern border
Rock River
299
Horicon Marsh, Wisconsin
Mississippi River
Pecatonica River, Kishwaukee River
Flows through Rockford; supports local recreation
Fox River
202
Big Lake, Wisconsin
Illinois River
Nippersink Creek
Flows through Aurora and Elgin; important for ecosystems
Des Plaines River
133
Southern Wisconsin
Illinois River
Salt Creek
Flows through Chicago suburbs; part of the Illinois Waterway
Kankakee River
133
South Bend, Indiana
Illinois River
Iroquois River
Known for scenic landscapes and recreational activities
Little Wabash River
240
Effingham County, Illinois
Wabash River
Skillet Fork
Primarily flows through rural southern Illinois
Big Muddy River
156
Jefferson County, Illinois
Mississippi River
None
Flows through southern Illinois; supports agriculture
Sangamon River
246
McLean County, Illinois
Illinois River
Salt Creek
Flows through Springfield; historically significant
Lakes of Illinois
Lake Name
Surface Area (Acres)
Location
Type
Primary Uses
Notable Features
Lake Michigan
14,000,000 (total lake area)
Northeast Illinois (Chicago)
Natural
Shipping, recreation, water supply
Part of the Great Lakes; only Great Lake in Illinois
Carlyle Lake
26,000
Clinton County
Man-made
Recreation, flood control
Largest man-made lake in Illinois
Rend Lake
18,900
Franklin and Jefferson Counties
Man-made
Recreation, wildlife habitat, water supply
Important for fishing and outdoor activities
Lake Shelbyville
11,100
Shelby and Moultrie Counties
Man-made
Flood control, recreation
Known for camping and boating
Fox Lake
2,710
Lake County
Natural
Recreation
Part of the Chain O'Lakes, a popular tourist destination
Clinton Lake
4,895
DeWitt County
Man-made
Cooling, recreation
Supports Clinton Nuclear Power Station
Lake Springfield
4,260
Sangamon County
Man-made
Water supply, recreation
Main water source for Springfield
Lake Decatur
3,093
Macon County
Man-made
Water supply
Supplies water for the city of Decatur
Shabbona Lake
318
DeKalb County
Man-made
Recreation, fishing
Known for excellent fishing opportunities
Lake Mattoon
1,050
Coles County
Man-made
Recreation, water supply
Provides water to Mattoon and surrounding areas
List of High Points and Elevated Areas in Illinois
Feature Name
Elevation (Feet)
Location
Type
Notable Features
Charles Mound
1,235
Jo Daviess County
High Point
Highest natural point in Illinois; located on private property but open to visitors on select weekends
Chestnut Mountain
1,020
Near Galena
Resort Area
Home to a ski resort overlooking the Mississippi River
Starved Rock
672
LaSalle County
Bluff
Famous for its scenic views, waterfalls, and hiking trails
Buffalo Rock
660
LaSalle County
Bluff
Overlooks the Illinois River; significant for its historical and geological importance
Ferne Clyffe Bluff
800
Johnson County
Bluff
Located in Ferne Clyffe State Park; known for its picturesque cliffs
Hicks Dome
980
Hardin County
Geological Feature
A unique geological uplift in the Shawnee Hills region
Shawnee Hills
Varies (Up to 1,000)
Southern Illinois
Hill Range
A region of rolling hills, forests, and unique rock formations
LaSalle Canyon
650
Starved Rock State Park
Canyon
Known for its steep walls and seasonal waterfalls
Plains in Illinois
Plain Name
Location
Type
Features
Significance
Central Plains
Spans across central Illinois
Alluvial Plain
Flat, fertile farmland with some rolling hills
Forms part of the Corn Belt; essential for agriculture
Great Mississippi River Floodplain
Along the Mississippi River, western Illinois
Floodplain
Low-lying areas with periodic flooding
Supports wetlands, agriculture, and river ecosystems
Illinois River Valley
Central Illinois, along the Illinois River
Alluvial Plain
Wide valley with rich soils and river terraces
Important for agriculture and trade
Wabash River Floodplain
Eastern Illinois, along the Wabash River
Floodplain
Flatlands with wetlands and fertile soils
Supports biodiversity and farming
Southern Illinois Plains
Southern Illinois
Alluvial and Loess Plain
Gently rolling terrain with some forested areas
Known for diverse agriculture and Shawnee Hills proximity
Driftless Area Plains
Northwest Illinois
Glacial Plain
Undulating terrain bypassed by glaciers
Unique geology and ecology, with scenic hills
Kankakee Plain
Northeast Illinois
Prairie Plain
Flat, sandy soils with prairie remnants
Once part of vast tallgrass prairie; ecological significance
Plateaus in Illinois
Plateau Name
Location
Elevation Range (Feet)
Type
Features
Significance
Shawnee Hills Plateau
Southern Illinois
400–1,000
Dissected Plateau
Forest-covered hills and ridges; sandstone bluffs
Part of the Shawnee National Forest; known for hiking and natural beauty
Mississippi River Bluffs
Western Illinois, along the Mississippi River
400–800
Escarpment/Plateau Edge
Steep cliffs overlooking the river; forested slopes
Ecological and scenic importance; supports diverse wildlife
Driftless Area Plateau
Northwest Illinois
600–1,200
Unglaciated Plateau
Hilly terrain with karst topography and valleys
Bypassed by glaciers; unique geological features
Salem Plateau (Extension)
Southern Illinois (extends from Missouri)
400–800
Geological Plateau
Rolling hills with limestone and dolomite bedrock
Rich in caves and springs; part of the Ozark Plateau system
Illinois River Bluffs
Central Illinois, along the Illinois River
400–600
Bluff/Plateau Edge
Elevated ridges with steep slopes
Important for agriculture and scenic beauty
Illinois Physical Features
Illinois, located in the Midwestern region of the United States, spans 57,914 square miles, making it the 25th largest state in the country. Its physical geography is characterized by expansive plains, rolling hills, and significant water bodies. While the state is known for its flat terrain, it also features regions of higher elevation, river valleys, and rich ecosystems that support agriculture, industry, and recreation.
Landforms
Central Plains
The Central Plains dominate Illinois's landscape, covering nearly 90% of the state. These plains are part of the larger Corn Belt, characterized by fertile soils and gently rolling terrain. The agricultural productivity of this region makes Illinois a leading state in corn and soybean production.
Driftless Area
Located in the northwest corner of Illinois, the Driftless Area features rugged terrain with hills, valleys, and bluffs. This region was bypassed by glaciers during the last Ice Age, resulting in unique geological formations and karst topography.
Shawnee Hills
In southern Illinois, the Shawnee Hills rise above the surrounding plains, reaching elevations of up to 1,235 feet at Charles Mound, the state's highest natural point. This region is covered in dense forests and is part of the Shawnee National Forest, known for its biodiversity and recreational opportunities.
Mississippi River Bluffs
Along the western border, steep bluffs rise above the Mississippi River, providing stunning views and supporting unique ecosystems. These bluffs are important for wildlife habitats and erosion control.
Water Bodies
Rivers
Illinois is home to several major rivers that play vital roles in transportation, ecology, and commerce. The Mississippi River forms the state's western boundary and serves as a key waterway for agricultural exports. The Illinois River, stretching 273 miles, connects Chicago to the Mississippi and is essential for inland shipping. The Ohio River forms the southeastern boundary and supports navigation and energy production.
Lakes
The northeastern corner of Illinois is bordered by Lake Michigan, one of the Great Lakes. This freshwater lake is crucial for transportation, recreation, and as a water supply. Other notable lakes include Carlyle Lake, the largest man-made lake in Illinois, and Rend Lake, known for fishing and wildlife habitats.
Climate and Vegetation
Illinois has a humid continental climate, with hot summers and cold winters. Average annual precipitation ranges from 35 inches in the north to 48 inches in the south. This climate supports diverse vegetation, from tallgrass prairies in the northern and central regions to forests in the south. While much of the prairie has been converted to farmland, conservation efforts are preserving remnants of these ecosystems.
Natural Resources
Illinois is rich in natural resources, including fertile soils, coal deposits, and freshwater reserves. The state ranks among the top coal-producing states, with vast reserves in the southern region. Its fertile plains are among the most productive agricultural lands in the world.
Geological Features
Illinois's geological history is shaped by glacial activity, which flattened much of the state's landscape and left behind rich alluvial soils. The state's eastern region contains loess deposits, windblown sediment that contributes to the fertility of the farmland.
Recreational and Cultural Significance
The physical features of Illinois provide opportunities for outdoor activities such as hiking, boating, and fishing. Regions like the Shawnee National Forest and Starved Rock State Park attract visitors with their scenic beauty and geological wonders. The Mississippi River and its bluffs are integral to the state's cultural and historical identity.
