From the Guide to 2010 State and Local Census Geography – Illinois – History:
The area of Illinois was part of the original territory of the United States, being part of lands ceded by four states to the United States and designated in 1787 as the "Territory northwest of the River Ohio." Illinois Territory was organized on February 3, 1809, from the western part of Indiana Territory, and included all of present-day Illinois, most of Wisconsin, the western part of the Upper Peninsula of Michigan and northeastern Minnesota.
Although the territory had not yet been legally established, census data for Illinois are available beginning with the 1800 census. The 1810 population is for the entire area of the Illinois Territory, including territory not in the present state. For an explanation of the revision to the 1800 population of Illinois, see Richard L. Forstall, Population of States and Counties of the United States: 1790-1990, Washington, DC: U.S. Government Printing Office, 1996, page 48.
Data for the legally established state of Illinois are available beginning with the 1820 census.
From Census.gov / Data:
Note: The dashboard above is cropped on the bottom. Click on the image for the full dashboard.
From data.census.gov:
Source: 2022 American Community Survey (ACS) 1-year estimates
Source: U.S. Census Bureau, Population Division (Annual Estimates of the Resident Population)
Source: 2018 - 2021 Annual Survey of Manufactures (ASM)
Source: 1978-2021 Business Dynamics Statistics (BDS)
Source: 2021 County Business Patterns (CBP)
Source: 2020 Annual Business Survey (ABS) Program
Source: 2020 Nonemployer Statistics (NES)
Note: Click on the image above to go to the Business Formation Statistics data page. For the Illinois graphic, scroll down to “Interactive Graphs.” Click on the icon for “Monthly Business Applications by State (BA)” and select “Illinois” in the upper-right drop-down area.
From Business and Economy > International Trade Data:
Note: After you create an account, you can choose between State Export Data (Origin of Movement) or State Import Data (State of Destination) by Harmonized System (HS) or NAICS. More information is available in the Quick Start Guide.
Source: Monthly State Retail Sales.
From the State Data Center (SDC) Program:
From the Library / America Counts: Stories Behind the Numbers:
From Census.gov / History:
From the Statistics in Schools (SIS) program:
Note: The Illinois page is cropped on the bottom. Click on the image above to go to the “State Facts for Students” main page. Use the drop down to select “Illinois” or click “IL” on the map for the full page for Illinois.
Source: 2017 Economic Census.