Illinois' Natural Divisions
Wisconsin Driftless Division (no sections in this division)
Rock River Hill Country Division
Freeport Section - The Freeport Section includes most of the Rock River
Hill Country Division. It is characterized by rolling hills and the presence
of dolomite and limestone bedrock. Limestone caves are present.
Oregon Section - The Oregon Section has sandstone bedrock and distinctive
plants, including ground pine, rusty woodsia and oak fern. These plants
are more commonly found in areas farther north in the United States.
Northeastern Morainal Division
Morainal Section - This section contains the moraines and related geologic
features resulting from late advances in the Wisconsinian glaciation period.
Most of Illinois' glacial lakes and peatlands are found here.
Lake Michigan Dunes Section - The Lake Michigan Dunes Section is distinctive
for its unique plants that grow on the dunes and beaches. Plant succession
from shifting sand to stabilized sand results in a variety of species.
Beach grass, trailing juniper and bearberry are three examples.
Chicago Lake Plain Section - This flat, poorly-drained area is composed
of the lake bed sediments of glacial Lake Chicago. Long ridges of shore-deposited
sands are conspicuous features. A few natural lakes exist near Calumet
City. The original vegetation of this section was prairie and marsh with
scrub-oak forests on sandy ridges.
Winnebago Drift Section - The Winnebago Drift Section includes gravel
hill prairies that once extended along the east bluffs of the Rock River
valley into Wisconsin. The section has fairly good drainage. Wet prairies
and marshes exist in the sand area along Coon Creek. The prairies contain
many plant species which are more common in prairies further west of Illinois.
Grand Prairie Division
Grand Prairie Section - This section includes the part of Illinois that
was affected by the late stages of the Wisconsinian glaciation, that is
outside the Northeastern Morainal Division and that does not include outwash
and sand areas. The Shelbyville and Bloomington moraines form the boundaries
of this section. Black-soil prairie, marshes and prairie potholes are
common in this poorly-drained area. The Kankakee mallow is found in this
section, growing only on an island in the Kankakee River.
Springfield Section - The Springfield Section is part of the area covered
by the Illinoian glaciation. Prairies grew on this land in presettlement
times. It has better drainage than the younger Grand Prairie Section.
Deep loess (a wind-blown silt) deposits support dry hill prairies along
the lower Sangamon River. Large areas of floodplain forest grow in the
valley of the lower Sangamon River and its tributaries.
Western Section - The Western Section was covered by the Illinoian glaciation.
This well-drained land was predominantly prairie in presettlement times.
Green River Lowland Section - The valley of the Green River and the
lower Rock River was formed by glacial meltwaters. Much glacial outwash
was deposited, and sand flats and dunes developed. The section originally
had many marshes and wet prairies. Scrub-oak forests grew on the sandy
ridges, and floodplain forests were present along the rivers. Sand prairies
were found on the sand flats and dunes. Most of this section has been
disturbed by grazing, cultivation and drainage.
Kankakee Sand Area Section - The sand of the Kankakee Sand Area Section
was deposited by the Kankakee Flood during the later stages of the Wisconsinian
glaciation. Sand prairie and marsh were the predominant vegetation of
this section before the land was drained for cultivation. Scrub-oak forests
exist on drier sites. The primrose violet is restricted to this section
in Illinois. The clear, well-vegetated, sand-bottomed streams contain
fishes like the weed shiner, ironcolor shiner and least darter.
Upper Mississippi River and Illinois River Bottomlands Division
Illinois River Section - The Illinois Section of this division is characterized
by its backwater lakes and forest vegetation. Spring bogs exist along
the river bluffs.
Mississippi River Section - The Mississippi River Section is made of
several, separated bottomlands along the Mississippi River, from the Wisconsin
border to Calhoun County. Most of the prairies of this section have been
drained for agriculture. Forests are found along the river inside levees
and on river islands.
Illinois River and Mississippi River Sand Areas Division
Illinois River Section - This section differs from the Mississippi River
Section by the absence of several plant and animal species.
Mississippi River Section - This section has several plant and animal
species which are absent from the Illinois River Section including false
heather and rock spikemoss. Both of these plants form large mats that
stabilize dune blowouts.
Western Forest--Prairie Division
Galesburg Section - The Galesburg Section is the area of the Western
Forest-Prairie Division that lies north of the Illinois River valley.
At the time of settlement, there were about equal amounts of forest and
prairie in this section, with forests mainly along the tributaries to
the Illinois River.
Carlinville Section - The Carlinville Section of this division is the
land southeast of the Illinois River valley. Originally it was covered
mostly by forest, with prairie accounting for about 12 percent of the
Middle Mississippi Border Division
Glaciated Section - The topography of this area was modified by the
pre-Illinoian and Illinoian glaciation stages. Limestone underlies most
of this section and may often be seen in cliffs along the river bluffs.
Driftless Section - This area of the state is apparently unglaciated.
It has many sinkholes and sinkhole ponds.
Southern Till Plain Division
Effingham Plain Section - The Effingham Plain Section is a relatively
flat plain drained by the Kaskaskia River. It originally was mostly prairie.
Post oak flatwoods are characteristic of the uplands. Sanctuaries for
the greater prairie chicken exist in this section.
Mt. Vernon Hill Country Section - The Mt. Vernon Hill Country Section
has a rolling, hilly topography. Upland forests covered most of this section
in presettlement times.
Wabash Border Division
Bottomlands Section - The Bottomlands Section of this division encompasses
the bottomland forests, sloughs, marshes and oxbow lakes in the floodplains
of the Wabash River, Ohio River and their major tributaries. Bottomland
forests are the main vegetation type with wet prairie and marshes associated
with the sloughs.
Southern Uplands Section - The Southern Uplands Section contains the
dry and mesic upland forests on the bluffs along the Wabash River. Some
sandstone ravines support an unusual combination of plant species.
Vermilion River Section - The Vermilion River Section is characterized
by rugged topography and the beech-maple forests in the ravines along
the Vermilion River and its tributaries. The beech-maple forest represents
a climax, deciduous forest type of the northeastern United States, which
is found in Illinois only in the extreme eastern and southern portions.
Northern Section - The Northern Section of the Ozark Division has limestone
bedrock, caves, sinkholes and a unique combination of plants and animals.
Plants found only in this section include stiff bedstraw and slender heliotrope.
They grow on hill prairies or exposed limestone ledges.
Central Section - The Central Section of this division has sandstone
bedrock. Its forest and other floral components are distinctive. Bradley's
spleenwort and Harvey's buttercup are species only in this section of
Southern Section - The Southern Section has significantly different
bedrock, topography, glacial history, forest composition and animals from
the other two sections in the division. Black spleenwort and shortleaf
pine are two of the unique plants found here.
Lower Mississippi River Bottomlands Division
Northern Section - The Northern Section is distinguished by its forest
composition, presence of wet prairies and marshes and absence of coastal
plain trees. The bottomlands of this section near East St. Louis are called
the "American Bottoms."
Southern Section - The bottomland forests of the Southern Section contain
a greater number of tree species than those found in the Northern Section
and also include some swamp species typical of the coastal plain.
Shawnee Hills Division
Greater Shawnee Hills Section - The Greater Shawnee Hills Section has
sandstone bedrock and distinctive plants. Filmy fern and French's shooting
star are unique plants in this section. French's shooting star may have
grown in this area since before glacial times. Ravines and ledges along
streams support plant species, like club mosses and sphagnum, which are
normally found in more northern areas of the Midwest.
Lesser Shawnee Hills Section - The Lesser Shawnee Hills Section has
limestone bedrock and sinkholes. The fluorspar deposits in Hardin County
are world famous. Caves are common in the limestone bluffs. Wild mock
orange is a distinctive plant.
Coastal Plain Division
Cretaceous Hills Section - This section is named for the fossil beds
from the Cretaceous period that are found in the rolling hills here. Also
present in the hills are sands, gravels and clays.
Bottomlands Section - The Bottomlands Section encompasses bottomland
forests, oxbow lakes, sloughs and rivers. This area includes the remnants
of the once vast bald cypress and tupelo gum swamps along the rivers.
Scientific Names Used on the Illinois' Natural Divisions Poster |
Glaciation in Illinois | References
for Illinois Natural Divisions Poster
Return to Illinois' Natural Divisions