Illinois Population Up 3.3 Percent in 2010 Census

Illinois Remains 5th Largest State in Nation Cook County Remains the 2nd Largest County in the Nation Chicago Remains 3rd Largest City in the Nation

Illinois' 2010 census results show over 12.8 million (12,830,632) people live in Illinois, up 3.3 percent since 2000. The 2010 Census had the most massive participation effort ever experienced in the country with 74 percent of households voluntarily returning their census forms by mail. Illinois' 76 percent participation rate was above the national average and due in part to collaborations with community organizations to promote participation in the Census throughout the state.

The Census is an important tool that ensures communities of every size get their fair share of funding for vital services and programs. It also provides accurate data to assist in developing effective plans for the future.

Cook County continues to have the highest population in the state and remains the second largest county in the U.S. with nearly 5.2 million residents, even with a decrease of 3.4 percent since 2000. This includes the nearly 2.7 million residents in the City of Chicago, which itself saw a 6.9 percent decrease from 2000.

The top five counties in Illinois based on population are:

Cook 5,194,675
DuPage 916,924
Lake 703,462
Will 677,560
Kane 515,269

The five largest cities in Illinois are:

Chicago 2,695,598
Aurora 197,899
Rockford 152,871
Joliet 147,433
Naperville 141,853

The five largest downstate counties are:

Winnebago 295,266
St. Clair 270,056
Madison 269,282
Champaign 201,081
Sangamon 197,465

The five largest downstate cities are:

Springfield 116,250
Peoria 115,007
Champaign 81,055
Bloomington 76,610
Decatur 76,122

According to the 2010 Census, Illinois had an increase of more than 650,000 minorities over the last decade. Asians experienced the largest increase, adding 163,331 residents since 2000, a 38.6 percent increase. People reporting two or more races on their census form increased by 54,966 or 23.4 percent. People reporting Hispanic or Latino origin increased by nearly 500,000 residents, or 32.5 percent. The voting age population in Illinois, people 18 years and over, increased by over 500,000 residents, or 5.8 percent.

The U.S. Census Bureau conducts the census every 10 years, as required by the U.S. Constitution. Beginning in early 2010, Census questionnaires were mailed or delivered to every household in the United States. In December 2010, the first results of the 2010 Census were announced. This included the total population count for each state, also known as apportionment data, which is used to determine the number of Congressional seats each state receives. Illinois lost one Congressional seat (from 19 to 18) because other states had greater population growth.

In mid-February 2011, data known as the redistricting data, were released. This is information that is more detailed and includes the first announcement of 2010 population counts for counties, townships, municipalities and small geographic units that allow state officials to realign congressional and state legislative districts as part of the redistricting process, taking into account population shifts since the last census and assuring equal representation for Illinois residents.

For more info on the 2010 Census, visit