DeWitt County is a county located in the U.S. state of Illinois. As of the 2010 census, the population was 16,561. Its county seat is Clinton. The county was formed on March 1, 1839, from Macon and McLean counties. The county was named in honor of the seventh Governor of New York State, DeWitt Clinton.
Winnebago County is a county located in the U.S. state of Illinois. According to the 2020 census, it had a population of 285,350 making it the seventh most populous county in Illinois behind Cook County and its five surrounding collar counties. Its county seat is Rockford. Winnebago County is the central county of the Rockford Metropolitan Statistical Area.
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.
Tazewell County is a county in the U.S. state of Illinois. According to the 2010 census, it had a population of 135,394. Its county seat and largest city is Pekin. It is pronounced with a short "a", to rhyme with "razz" rather than "raze".
St. Clair County is the oldest county in Illinois; its western border is formed by the Mississippi River, bordering Missouri. It is a part of the Metro East in southern Illinois. According to the 2020 United States Census, it had a population of 257,400, 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, from the western half of Knox County, before the establishment of Illinois as a state as the base for the Illinois Territory. Cahokia Village in the county was founded in 1697 and was a French settlement and former Jesuit mission.
Shelby County is a county located in the U.S. state of Illinois. According to the 2020 census, it had a population of 20,990. Its county seat is Shelbyville.
Rock Island County is a county located in the U.S. state of Illinois, bounded on the west by the Mississippi River. According to the 2010 census, it had a population of 147,546. Its county seat is Rock Island; its largest city is neighboring Moline. Rock Island County is one of the four counties that make up the Davenport-Moline-Rock Island, IA-IL Metropolitan Statistical Area.
Pulaski County is a county located in the U.S. state of Illinois. According to the 2020 census, it had a population of 5,193. Its county seat is Mound City. It is located along the Ohio River in the southwestern portion of the state, known locally as "Little Egypt".
Mason County is a county in the U.S. state of Illinois. According to the 2010 census, it had a population of 14,666. Its county seat is Havana. The county is named in honor of George Mason, a member of the Virginia legislature who campaigned for the adoption of the United States Bill of Rights.
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. Kankakee County comprises the Kankakee, IL Metropolitan Statistical Area.
Fayette County is a county located in the U.S. state of Illinois. As of the 2010 census, the population was 22,140. Its county seat is Vandalia. Ramsey Lake State Recreation Area is located in the northwest part of this county.
Cumberland County is a county located in the U.S. state of Illinois. As of the 2010 census, the population was 11,048. Its county seat is Toledo.
Christian County is a county located in the U.S. state of Illinois. As of the 2010 census, the population was 34,800. Its county seat is Taylorville. Christian County comprises the Taylorville, IL Micropolitan Statistical Area, which is also included in the Springfield-Jacksonville-Lincoln, IL Combined Statistical Area.
Brown County is a county located in the U.S. state of Illinois. As of the 2010 census, the population was 6,937. Its county seat is Mount Sterling.
Alexander County is the southernmost and southwesternmost county in the U.S. state of Illinois. As of the 2020 census, the population was 5,240. Its county seat is Cairo and its western boundary is formed by the Mississippi River.
Palos Park is a village in southwestern Cook County, Illinois, United States. Per the 2020 census, the population was 4,899.
Millstadt is a village in St. Clair County, Illinois, United States, located at the crossing of Illinois Routes 163 and 158. The village is known for its German heritage, with more than half its people of German descent. The population was 4,011 at the 2010 census, but a more recent study in July 2018 estimated the number at 3,885.
Cicero Township is one of 29 townships in Cook County, Illinois, USA. It is coextensive with the town of Cicero. As of the 2010 census, its population was 83,891.
The U.S. State of Illinois currently has 43 statistical areas that have been delineated by the Office of Management and Budget (OMB). On March 6, 2020, the OMB delineated 11 combined statistical areas, 13 metropolitan statistical areas, and 19 micropolitan statistical areas in Illinois.
Harmony is an unincorporated community and census-designated place in McHenry County, Illinois, United States. Harmony is located on U.S. Route 20, 5 miles (8.0 km) west-southwest of Huntley. It was named a CDP prior to the 2020 census which showed a population of 20.
United States 
Illinois 
St. Clair 
