Illinois Geography

Abbreviated as IL by ABBREVIATIONFINDER, Illinois is bordered to the north by Wisconsin, to the northeast by Lake Michigan, to the east by Indiana, to the south by Kentucky (across the Ohio River), to the west by Iowa and Missouri (across the Mississippi River). Illinois also borders the state of Michigan, though only through a water boundary on Lake Michigan.

Illinois is 629 kilometers north-south and 340 kilometers east-west. The area of ​​the state is 149,998 km², of which 6,030 (4%) are covered by water. The State is the twenty-fifth largest State in the country (twenty-fourth if we do not count the bodies of water). The Illinois coastline with Lake Michigan is 101 kilometers long.

Although Illinois is located entirely in the Interior Plains, it is divided into three essential geographic regions. The first is Chicagoland, which includes the city of Chicago, its suburbs, and the adjacent suburban area, through which the metropolis is expanding. This region includes several counties in Indiana and Wisconsin, and stretches across much of northern Illinois, toward the Iowa border, on the strip between Interstates 80 and 90. This region is cosmopolitan, densely populated, highly industrialized, and inhabited by a wide variety of ethnic groups. Cook County is the most populous in the state, with more than 5.3 million residents in 2004.

To the south and west is the state’s second major division, central Illinois, a mostly flat prairie area. The western section (that is, west of the Illinois River) was originally part of the Military Treaty of 1812 and forms the distinctive western bulge of the state. Known as the Land of Lincoln or the Heart of Illinois, it is characterized by its small and medium-sized cities. Here agriculture has a strong presence, especially corn and soybeans, as well as educational institutions and factories. Important cities in this region include: Peoria (Illinois’ third-largest metropolitan area with 370,000 residents), Springfield (the state capital), Decatur, Bloomington-Normal, and Champaign-Urbana.

The third division is southern Illinois, which encompasses the entire area south of US Route 50, and includes the Little Egypt region, near the confluence of the Mississippi River with the Ohio River. This region is distinguished from the other two by its warmer climate, its different crops, its more rugged topography (the southernmost tip of the state did not suffer the effects of the Illinois Glaciation, nor of the previous ones), as well as its small oil fields and their coal mining. The region is slightly more populated than the central part of the state, and is centered in two areas. First, the Illinois suburbs of St. Louis comprise the second most populous metropolitan area in the state with almost 600,000 residents, and are popularly known as the Metro-East.

In the extreme northwest of Illinois, is the Driftless Area, a region that was not affected by the glaciations, and therefore with a higher and more rugged topography. Charles Mound, located in this region, is the highest natural elevation in the state, at 376 m. Formally speaking, the highest elevation in Illinois is that of the Sears Tower, with an altitude at the top of its roof of approximately 1,400 feet.


Illinois has a continental climate, with four distinct seasons, with hot summers and coldwinters. However, the weather varies quite a bit from season to season. Weather in Illinois is relatively unstable, and it can change suddenly, especially in winter. Sometimes the temperature can drop more than 12 ° C in just one hour. The main reason for this instability is the absence of geographical obstacles in the State and in its vicinity, which allow the rapid movement of air currents coming from any direction. Throughout the year, the average temperature drops as you travel north.

Average annual rainfall rates of rainfall vary from 100 centimeters in the north to 85 centimeters in the south. Average annual snowfall rates, meanwhile, range from 30 inches in the north to 10 inches in southern Illinois. The occurrence of tornadoes is very common (with peaks between April and June), in fact, tornadoes killed more people in Illinois than in any other American state. The most destructive of them, the Tri-State Tornado (Tristate Tornado, affecting Missouri, Illinois and Indiana) occurred in 1925, killing 695 people.


First Presbyterian Church, Chicago.

Religious Affiliations of the Illinois Population:

  • Christianity – 80%
    • Protestants – 49%
      • Baptist Church – 12%
      • Lutheran Church – 7%
      • Methodist Church – 7%
      • Presbyterian Church – 3%
      • Other Protestant affiliations – 20%
    • Catholics – 30%
    • Other Christian affiliations – 1%
  • Other religions – 4%
  • Non-religious – 16%

Protestants are the largest religious group in Illinois. However, unlike other states in the Midwest, such a religion does not clearly dominate. Roman Catholics, who are primarily concentrated in and around Chicago, comprise 30% of the population. The Chicago metropolitan area is home to the 3rd largest Jewish population in the United States.

  • CountryAAH: Offers a full list of cities and towns in Illinois, together with postal codes for each of them, and including capital city of Illinois.

Races and ethnicities

  • 8% White
  • 1% African Americans
  • 3% Hispanic
  • 4% Native Americans
  • 9% Two or more races

The five largest ethnic groups in Illinois are Germans (comprising 19.6% of the state’s population), African Americans (15.1%), Irish (12.2%), Mexicans (9.2%) and the Poles (7.5%).

About three in ten whites in the state say they have at least some German ancestry, making Germans the largest ethnic group in the state. African Americans are present in large numbers in Chicago, East St. Louis, and the southern tip of Illinois. The descendants of indigenous natives and the British are concentrated mainly in the southeast of the state. The Chicago metropolitan region is home to large numbers of Irish, Mexican and Polish people. Other ethnic backgrounds are the English, Italians, and Swedes.

About 86.7% of the state’s population was born in the country. The other 13.3% were born outside the country, that is, they are immigrants. Most of the immigrants settle in the Chicago metropolitan area. Mexicans comprise approximately 40% of the immigrant population, while Poles comprise 10%.

Illinois state