Illinois

I

Introduction

Illinois, state in the north central United States, in the heart of the Midwest. Illinois was little more than a vast wilderness 200 years ago. Since entering the Union on December 3, 1818, as the 21st state, the economy of Illinois has expanded until today Illinois is one of the most productive agricultural and industrial states in the Union, and its economic influence now extends far beyond the Midwest.

Flanked by the Mississippi River on the west and by a short stretch of Lake Michigan on the northeast, the state is largely an area of flat or gently rolling plains that were once covered by tall luxuriant prairie grasses. The grasslands have long since been cleared for raising crops, but the state still retains its nickname, the Prairie State. Much of the land is tidily laid out in the checkerboard pattern so typical of the Midwest. Large prosperous farms specialize in raising grain and livestock on the rich prairie soils. Tall grain elevators, church spires, and an occasional grove of trees are the most conspicuous landmarks; and machine sheds, fields of corn and soybeans, and hogs in feedlots are the most common sights across the farmlands.

Rural Illinois does not lack physical and agricultural diversity. It has hill lands and a national forest in the south, cotton fields on the fertile alluvial lands in the extreme south, scenic bluffs along the Mississippi, and hillside dairy farms in the northwest.

In addition, rural Illinois is far from being isolated from urban Illinois. The state is covered by a dense network of railroads, highways, waterways, and air routes, most of which converge on the great metropolis of Chicago. The third largest city in the United States, Chicago dominates the industrial, financial, and social life of the state. In some ways, Chicago stands apart from the rest of the state. To many Chicagoans, Illinois consists of two sections: Chicago and “downstate.” Other Illinois cities, such as Peoria, Rockford, and Decatur, tend to be overshadowed by Chicago. Nevertheless, these smaller communities manage to retain their distinctive characteristics. Perhaps the most famous is the state capital, Springfield, which President Abraham Lincoln often referred to as his home. The national fame of Springfield, New Salem, and other places in Illinois that are associated with Lincoln are reflected in the official state slogan, Land of Lincoln.

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The state is named for the Illinois, or Illini, a confederation of Native Americans of various tribes who inhabited Illinois and other sections of the Midwest at the time the first French explorers entered the region. The name Illinois is said to have been a French version of the Illini word for themselves, “Illiniwek.”

II

Physical Geography

Illinois ranks 25th in size among the states of the Union, with an area of 149,997 sq km (57,914 sq mi). That includes 1,958 sq km (756 sq mi) of inland water and 4,079 sq km (1,575 sq mi) of Lake Michigan over which the state has jurisdiction. The greatest north-to-south dimension of the state is 610 km (379 mi), and the greatest east-to-west distance is 343 km (213 mi). The mean elevation is about 180 m (600 ft).

A

Natural Regions

Illinois includes parts of four major natural regions, or physiographic provinces, of the United States: the Central Lowland, the Interior Low Plateaus, the Ozark Plateaus, and the Gulf Coastal Plain. The extensive flatlands of the Central Lowland occupy nearly all of Illinois, whereas the other three regions cover only small areas of the state. The Interior Low Plateaus and the Ozark Plateaus form a strip of hilly land across the southern part of the state. The flat alluvial lands of the Gulf Coastal Plain cover a small section of extreme southern Illinois.

The Central Lowland and the Interior Low Plateaus are subdivisions of a broader region known as the Interior Plains. The Ozark Plateaus form a section of the larger Interior Highlands region, and the Gulf Coastal Plain is part of the Coastal Plain.

The Central Lowland covers all but a small area of Illinois. Most of the Central Lowland is a level or slightly undulating plain, crossed here and there by broad, low ridges. The flatness of the land is a result of glacial action that occurred during the last Ice Age, which ended about 10,000 years ago, when great ice sheets advanced and retreated across the region. After the ice eventually retreated northeastward, the old preglacial landscape was left buried under a thick cover of glacial deposits, called drift, or glacial drift. Much of the drift is made up of clay and boulders, which together are called till, and form moraines. The so-called Till Plains form the typical flat farmlands of Illinois. The fertile Till Plains area of east central Illinois is known as the Grand Prairie. The low ridges found in some areas are terminal moraines that were piled up during the periods of glaciation by stagnant ice sheets.

In some areas, especially in the Grand Prairie and in south central Illinois, the land is so flat that the taller buildings of cities on the plain can be seen for great distances across country. Partly because of the flatness, rainwater does not readily drain away, and before ditches and drains were dug, much of the land was swampy for at least part of the year. There are still large tracts of such wetland along the Wabash, Kaskaskia, and Big Muddy rivers today. Farther west, between the Illinois and Mississippi rivers, lie the Quincy hills, which are broken by deeply cut stream valleys. The extreme northwest is also an area of hills. Together with neighboring sections of Wisconsin and Iowa it forms the Driftless section, or Wisconsin Driftless section. Only the earliest of the ice sheets covered this section, and nearly all of the drift deposited has long since been eroded. Charles Mound, which is 376 m (1,235 ft) above sea level and the highest point in Illinois, lies on a long hilly ridge in the Driftless section. However, this is only 180 to 210 m (600 to 700 ft) above the general level of the Grand Prairie and much of the rest of the state.

The Interior Low Plateaus portion of southern Illinois was not covered by the ice sheets, and its high ridges and bluffs afford magnificent panoramic views across the lowlands. Much of the region is now part of Shawnee National Forest.

The Ozark Plateaus cover a small section of southwestern Illinois. Much of the land is forested and is too rugged and rocky for farming. Limestone, which is soluble in water, underlies much of the region, and small depressions, known as sinkholes, are found where the limestone has been dissolved.

The Gulf Coastal Plain, at the southern tip of Illinois, is an extremely flat area where the land has been built of alluvial deposits from the Ohio and Mississippi rivers. Much of the region is cultivated and is very productive. Because of the fertile soils and the great river there, early settlers in this section of Illinois gave the region the nickname Little Egypt.

B

Rivers and Lakes

Except for a few short streams flowing into Lake Michigan, nearly all the streams and rivers of Illinois drain westward or southward to the Mississippi River or to the Ohio River, which joins the Mississippi near Cairo in the extreme south. The Mississippi forms the western boundary of the state. Its tributaries in Illinois include the Illinois, Rock, Kaskaskia, and Big Muddy rivers. The Ohio River’s chief tributary in Illinois is the Wabash River. The Embarras and Little Wabash rivers are tributaries of the Wabash.

The largest river entirely within the state is the Illinois River, which is formed by the junction of the Kankakee and Des Plaines rivers. It flows for 680 km (420 mi) across the state before joining the Mississippi River at Grafton. The Illinois has been deepened and straightened and forms part of the Illinois Waterway.

The watershed between rivers that flow into the Mississippi river system and rivers that flow into the Great Lakes is low and in many places is not easily discernible. In what is now the Chicago area, explorers had little difficulty portaging, or carrying, their canoes over the low watershed between the Des Plaines River, which flows into the Illinois, and the Chicago River, which then flowed into Lake Michigan. In 1900 the Chicago River’s flow was reversed to make it carry and dilute the city’s sewage and industrial wastes into the Illinois River, instead of into Lake Michigan, the source of the city’s drinking water.

Except for Lake Michigan, which borders the state on the northeast, there are no large natural lakes in Illinois. Small natural lakes, all in the northern part of the state, include Clear, Crane, Fox, Goose, Grass, Peoria, Pistakee, and Ringwood lakes. The largest artificially created bodies of water within Illinois include Rend Lake, which is held back by a dam on the Big Muddy River, and Carlyle Lake, on the Kaskaskia River near Carlyle.