In the 2010 Census, Illinois was found to have a population of 12,830,632, representing a slightly lower increase than had been anticipated in estimates from two years earlier.
Specific demographic data from the 2010 Census is not subject to release until March 2011, but as of the 2007 estimates from the U.S. Census Bureau, there were 1,768,518 foreign-born inhabitants of the state or 13.8% of the population, with 48.4% from Latin America, 24.6% from Asia, 22.8% from Europe, 2.9% from Africa, 1.2% from Northern America and 0.2% from Oceania. Of the foreign-born population, 43.7% were naturalized U.S. citizens and 56.3% were not U.S. citizens. Additionally, the racial distributions were as follows: 65.0% European American, 15.0% African American, 14.9% Latino American, 4.3% Asian American, 0.3% American Indian and Alaska Natives, and 0.1% Native Hawaiians and Pacific Islander American. In 2007, 6.9% of Illinois' population was reported as being under age 5, 24.9% under age 18 and 12.1% were age 65 and over. Females made up approximately 50.7% of the population.
According to the 2007 estimates, 21.1% of the population had German ancestry, 13.3% had Irish ancestry, 7.9% had Polish ancestry, 6.7% had English ancestry, 6.4% had Italian ancestry, 4.6% listed themselves as American, 2.4% had Swedish ancestry, 2.2% had French ancestry, other than Basque, 1.6% had Dutch ancestry, 1.4% had Norwegian ancestry and 1.3% had Scottish ancestry. Also, 21.8% of the population age 5 years and over reported speaking a language other than English, with 12.8% of the population speaking Spanish, 5.6% speaking other Indo-European languages, 2.5% speaking Asian and Austronesian languages, and 0.8% speaking other languages.
Chicago, along the shores of Lake Michigan, is the nation's third largest city. In 2000, 23.3% of Illinois' population lived in the city of Chicago, 43.3% in Cook County and 65.6% in the counties of the Chicago metropolitan area: Will, DuPage, Kane, Lake and McHenry counties, as well as Cook County. The remaining population lives in the smaller cities and rural areas that dot the state's plains. As of 2000, the state's center of population was at , located in Grundy County, northeast of the village of Mazon.