Illinois is a state in the Midwestern and Great Lakes Regions of the United States. It has the fifth largest gross domestic product (GDP), the sixth largest population, and the 25th largest land area of all U.S. states. Illinois has been noted as a microcosm of the entire United States. With Chicago in northeastern Illinois, small industrial cities and immense agricultural productivity in the north and center of the state, and natural resources such as coal, timber, and petroleum in the south, Illinois has a diverse economic base, and is a major transportation hub. Chicagoland, Chicago's metropolitan area, encompasses over 65% of the state's population. The Port of Chicago connects the state to international ports via two main routes: from the Great Lakes, via the Saint Lawrence Seaway, to the Atlantic Ocean and from the Great Lakes to the Mississippi River, via the Illinois Waterway to the Illinois River. The Mississippi River, the Ohio River, and the Wabash River form parts of the boundaries of Illinois. For decades, Chicago's O'Hare International Airport has been ranked as one of the world's busiest airports. Illinois has long had a reputation as a bellwether both in social and cultural terms and, through the 1980s, in politics.
Will County is a county in the northeastern part of the state of Illinois. According to the 2010 census, it had a population of 677,560, an increase of 34.9% from 502,266 in 2000, making it Illinois's fourth-most populous county. The county seat is Joliet.
Warren County is a county in the U.S. state of Illinois. According to the 2010 census, it had a population of 17,707. Its county seat is Monmouth.
Stephenson County is a county located in the U.S. state of Illinois. According to the 2010 United States Census, it had a population of 47,711. Its county seat is Freeport.
St. Clair County is the oldest county in the U.S. state of Illinois; its western border is formed by the Mississippi River, bordering the U.S. state of Missouri. It is a part of the Metro East in southern Illinois. According to the 2010 United States Census, it had a population of 270,056, making it the eighth-most populous county in Illinois and the most populous in the southern portion of the state. Its county seat is Belleville. The county was founded in 1790 by the government of the Northwest Territory, before the establishment of Illinois as a state. Cahokia Village in the county was founded in 1697 and was a French settlement and former Jesuit mission.
Sangamon County is a county located in the center of the U.S. state of Illinois. According to the 2010 census, it had a population of 197,465. Its county seat and largest city is Springfield, the state capital.
Randolph County is a county located in the U.S. state of Illinois. According to the 2010 census, it had a population of 33,476. Its county seat is Chester.
Peoria County is a county in the U.S. state of Illinois. The 2010 United States Census listed its population at 186,494. Its county seat is Peoria.
Livingston County is a county located in the U.S. state of Illinois. According to the 2010 census, it has a population of 38,950. Its county seat is Pontiac.
Lake County is a county situated in the northeastern corner of the U.S. state of Illinois along the shores of Lake Michigan. According to the 2010 census, it has a population of 703,462, making it the third-most populous county in Illinois after nearby Cook and DuPage Counties. Its county seat is Waukegan, the ninth-largest city in Illinois. Due to its location, immediately north of Chicago’s Cook County, Lake County is one of the collar counties of the Chicago metropolitan area.
Knox County is a county in the U.S. state of Illinois. According to the 2010 census, it had a population of 52,919. Its county seat is Galesburg.
Kankakee County is a county located in the U.S. state of Illinois. According to the 2010 census, it has a population of 113,449. Its county seat is Kankakee.
Kane County is a county in the U.S. state of Illinois. According to the 2010 census, it has a population of 515,269, making it the fifth-most populous county in Illinois. Its county seat is Geneva, and its largest city is Aurora.
Edwards County is a county located in the U.S. state of Illinois. As of the 2010 census, the population was 6,721. Its county seat is Albion. It is located in the southern portion known locally as "Little Egypt".
DeKalb County is a county located in the U.S. state of Illinois. As of the 2010 United States Census, the population was 105,160. Its county seat is Sycamore.
Cook County is the most populous county in the U.S. state of Illinois and the second-most-populous county in the United States after Los Angeles County, California. As of 2018, the population was 5,180,493. Its county seat is Chicago, the most populous city in Illinois and the third-most-populous city in the United States. More than 40% of all residents of Illinois live in Cook County.
Alexander County is the southernmost county of the U.S. state of Illinois. As of the 2010 census, the population was 8,238. Its county seat is Cairo and its western boundary is formed by the Mississippi River.
The Chicago metropolitan area, or Chicagoland, is the metropolitan area that includes the city of Chicago, covering 14 counties in the U.S. states of Illinois, Indiana, and Wisconsin. With an estimated CSA population of roughly 10 million people and an MSA population of 9.5 million people, it is the third largest metropolitan area in the United States.
