The 2015 Census estimates put the population at 12,859,995, which was a decrease from the 2014 numbers. Illinois is one of only 7 states that has a negative growth rate in 2016. At -0.17% per year, it is ahead of only West Virginia. Between 2000 and 2010, the population of Illinois grew by a mere 3.3%, compared to the national average US population growth of 9.7%.
The 2018 population estimates Illinois is the sixth largest state in the USA based on population.
Most of the Illinois population is heavily concentrated in the North East of the state in the metropolitan area of Chicago. Chicago, which is home to 2,720,546 people, remains the largest city in Illinois. This city dwarfs the state's other cities, including the capital of the state. The next largest is Aurora, with 200,661 people.
This marks one of Illinois' defining features -- although it has a large urban population, it is spread through a number of smaller cities. Including Chicago, there are twelve cities (including the city of Springfield, the state's capital) with more than 75,000 people.
Many of these smaller cities make up a part of the Chicago Metropolitan Area (prosaically also known as Chicagoland), which holds between 8.3 and 9.8 million people, depending on how you classify its boundaries.
Cook County is the largest county in Illinois, housing 5,238,216 people. The next largest county is neighboring Dupage, with 933,736 people. Almost half of the Illinois population can be found in just those two counties.
The median age in Illinois is 37.4 years of age, with a slight gender difference over the state- 50.9% female and 49.1% male.
In religious terms, Illinois shows its preferences with a 71% preference for Christian based faiths, a 6% affiliation with non-Christian based faiths, and 22% of the population being unaffiliated with any particular religion.
Illinois was included in the Northwest Territory established in 1787 and then in Indiana Territory (1800). Illinois Territory was established in 1809, and included virtually all of present-day Wisconsin and portions of Minnesota and the Upper Peninsula of Michigan. Illinois was admitted as a State on December 3, 1818 with essentially its present boundaries.
In 1790 the Northwest Territory had no census coverage. The population shown for 1800 is the total of two counties and one community in present-day Illinois, at that time part of Indiana Territory. Knox County, Indiana Territory, also included some population in what is now Illinois. In 1810, the returns for the two counties of Illinois Territory included some settlements in present-day Wisconsin. The northern part of the State was not fully covered by the census until 1830.
According to the most recent ACS, the racial composition of Illinois was:
Illinois saw massive growth throughout the 19th century, from a measly 2,458 people in 1800 to nearly 5 million in 1900. This rise made Illinois the 3rd largest state by the turn of the century. Growth continued into the 20th century, albeit at a slower pace.
In Illinois' cities, population growth has stalled. Chicago was, for much of its early history, one of America's fastest growing cities. Between 1850 and 1930, the city grew by at least 25% each decade, and in some decades it doubled or even tripled in size. However, from the 1960s onwards, Chicago has been steadily shrinking and a city which was home to 3.5 million people in 1960 is home to just 2.7 million today.
If the current decline continues, Illinois will fall back to the 6th spot in state rankings at the 2020 Census, behind Pennsylvania.
Some estimates expect Illinois to see growth again by 2020, and possibly reach 13.1 million in 2020.
Based on data from the 2010 Census, Illinois has the 14th highest percentage of African Americans across all states. Based on 2011 data, the state also has the 5th highest Hispanic population in the country with over 2 million Hispanic residents, and the 10th highest percentage of Hispanics that account for its diverse total population.
In recent years, Illinois has seen significant declines in its white population, with numbers dropping from 83.5% of the total population in 1970 to 63.3% just 40 years later. According to 2011 data, almost 50% of the population under the age of 1 were minorities.
According to data from 2007, over 1.7 million people in Illinois were foreign-born. This represented, at the time, almost 14% of the population. Over 48% of Illinois' foreign-born inhabitants came from Latin America, while almost one-quarter of the total number came from Asia. It is estimated that over 58% of the total 1.7 million foreign-born inhabitants recorded were not US citizens.
When looking at population growth of the state of Illinois by county, the data show that the majority of counties have seen population declines. However, there were still a handful of counties that saw small rates of growth, based on data taken from the 2010 Census and again during 2015 estimates taken by the US Census Bureau. During this 5-year period, Kendall County exhibited the most growth at a rate of 6.98%. Other counties that saw growth during this time period include Kane County at 2.86%, Champaign at 3.66%, and Monroe at 2.63%.
There were far more counties that experienced declines in population. This includes Alexander County, which by far had the biggest decline percentage at over 17%. Other counties with declining populations include Mason at 6.49%, Livingston at 5.66%, and Cass at 5.77%, among others.
Black or African American
Two or more races
Native Hawaiian or Pacific Islander
Average Family Size
Average Household Size
Rate of Home Ownership
Less Than 9th Grade
9th to 12th Grade
High School Graduate
High School Graduation Rate
The highest rate of high school graduation is among white people with a rate of 83.02%.
The highest rate of bachelors degrees is among asian people with a rate of 56.98%.
Other Indo-European Languages
Asian and Pacific Island Languages
76.76% of Illinois residents speak only English, while 23.24% speak other languages. The non-English language spoken by the largest group is Spanish, which is spoken by 13.48% of the population.
Overall Poverty Rate
Male Poverty Rate
Female Poverty Rate
The race most likely to be in poverty in Illinois is Black, with 24.69% below the poverty level.
The race least likely to be in poverty in Illinois is White, with 8.29% below the poverty level.
The poverty rate among those that worked full-time for the past 12 months was 2.13%. Among those working part-time, it was 14.27%, and for those that did not work, the poverty rate was 20.39%.
Overall Marriage Rate
Male Marriage Rate
Female Marriage Rate
The age group where males are most likely to be married is Over 65, while the female age group most likely to be married is 45-54.
Second Gulf War
First Gulf War
World War II
Less Than 9th Grade
High School Graduate
Bachelors or Greater
Veteran Poverty Rate
Veteran Disability Rate
Labor Force Participation
Non citizens include legal permanent residents (green card holders), international students, temporary workers, humanitarian migrants, and illegal immigrants.
Born in Illinois
87.94% of Illinois residents were born in the United States, with 68.69% having been born in Illinois. 6.82% of residents are not US citizens. Of those not born in the United States, the largest percentage are from Latin America.