Data / Rankings / Population under 18 / Counties in Illinois

Counties in Illinois by population under 18

Kendall County had the highest population under 18 of 102 counties in 2017, at 29.5%. Brown County had the lowest, at 16.5%. The median was 22% and the figure for Illinois was 22.6%. Source: the U.S. Census Bureau.

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Highest29.5Kendall County
Lowest16.5Brown County
Median22102 counties
Illinois22.6History

Map of counties, 2017

Adams County: 22.4 %Alexander County: 23 %Bond County: 18.7 %Boone County: 25.7 %Brown County: 16.5 %Bureau County: 21.7 %Calhoun County: 20.9 %Carroll County: 18.3 %Cass County: 24.7 %Champaign County: 19.3 %Christian County: 20.4 %Clark County: 22.8 %Clay County: 22.5 %Clinton County: 21.7 %Coles County: 19.3 %Cook County: 21.7 %Crawford County: 20.1 %Cumberland County: 22.6 %DeKalb County: 22.4 %De Witt County: 21.8 %Douglas County: 25.3 %DuPage County: 22.8 %Edgar County: 21 %Edwards County: 22.7 %Effingham County: 23.2 %Fayette County: 21.1 %Ford County: 23 %Franklin County: 22 %Fulton County: 20.1 %Gallatin County: 21 %Greene County: 21.9 %Grundy County: 25.6 %Hamilton County: 22.7 %Hancock County: 21.2 %Hardin County: 18.1 %Henderson County: 19 %Henry County: 23 %Iroquois County: 22.1 %Jackson County: 19 %Jasper County: 22.5 %Jefferson County: 22.3 %Jersey County: 20.8 %Jo Daviess County: 19.5 %Johnson County: 17.9 %Kane County: 26 %Kankakee County: 23.3 %Kendall County: 29.5 %Knox County: 19.9 %Lake County: 24.6 %LaSalle County: 21.5 %Lawrence County: 19.2 %Lee County: 20.1 %Livingston County: 21.9 %Logan County: 19.6 %McDonough County: 18 %McHenry County: 23.8 %McLean County: 22.1 %Macon County: 22.2 %Macoupin County: 21.2 %Madison County: 21.8 %Marion County: 22.8 %Marshall County: 20.4 %Mason County: 20.4 %Massac County: 23 %Menard County: 22.8 %Mercer County: 21.9 %Monroe County: 22.8 %Montgomery County: 20.5 %Morgan County: 19.9 %Moultrie County: 25.3 %Ogle County: 23 %Peoria County: 23.5 %Perry County: 19.5 %Piatt County: 22.5 %Pike County: 22.4 %Pope County: 17.7 %Pulaski County: 22.1 %Putnam County: 20 %Randolph County: 20 %Richland County: 22.6 %Rock Island County: 22.2 %St. Clair County: 23.8 %Saline County: 22.4 %Sangamon County: 22.4 %Schuyler County: 19.1 %Scott County: 22 %Shelby County: 21.2 %Stark County: 22 %Stephenson County: 21.5 %Tazewell County: 23 %Union County: 20.5 %Vermilion County: 23.4 %Wabash County: 21.8 %Warren County: 21.7 %Washington County: 21.3 %Wayne County: 23.2 %White County: 21.3 %Whiteside County: 22.1 %Will County: 25.5 %Williamson County: 21.9 %Winnebago County: 23.3 %Woodford County: 24.7 %
  • Under 20
  • 20 to 21
  • 21 to 22
  • 22 to 23
  • 23 and over
%, 2017. Source: Invokely calculation with data from U.S. Census Bureau. Boundaries: U.S. Census Bureau cartographic boundary files.

Top 40 counties, 2017

Kendall County: 29.5 %Kendall County29.5Kane County: 26 %Kane County26Boone County: 25.7 %Boone County25.7Grundy County: 25.6 %Grundy County25.6Will County: 25.5 %Will County25.5Douglas County: 25.3 %Douglas County25.3Moultrie County: 25.3 %Moultrie County25.3Cass County: 24.7 %Cass County24.7Woodford County: 24.7 %Woodford County24.7Lake County: 24.6 %Lake County24.6McHenry County: 23.8 %McHenry County23.8St. Clair County: 23.8 %St. Clair County23.8Peoria County: 23.5 %Peoria County23.5Vermilion County: 23.4 %Vermilion County23.4Kankakee County: 23.3 %Kankakee County23.3Winnebago County: 23.3 %Winnebago County23.3Effingham County: 23.2 %Effingham County23.2Wayne County: 23.2 %Wayne County23.2Tazewell County: 23 %Tazewell County23Massac County: 23 %Massac County23Alexander County: 23 %Alexander County23Henry County: 23 %Henry County23Ford County: 23 %Ford County23Ogle County: 23 %Ogle County23DuPage County: 22.8 %DuPage County22.8Clark County: 22.8 %Clark County22.8Marion County: 22.8 %Marion County22.8Monroe County: 22.8 %Monroe County22.8Menard County: 22.8 %Menard County22.8Hamilton County: 22.7 %Hamilton County22.7Edwards County: 22.7 %Edwards County22.7Cumberland County: 22.6 %Cumberland County22.6Richland County: 22.6 %Richland County22.6Clay County: 22.5 %Clay County22.5Jasper County: 22.5 %Jasper County22.5Piatt County: 22.5 %Piatt County22.5Adams County: 22.4 %Adams County22.4Sangamon County: 22.4 %Sangamon County22.4DeKalb County: 22.4 %DeKalb County22.4Pike County: 22.4 %Pike County22.4Kendall County: 29.5 %Kendall County29.5Kane County: 26 %Kane County26Boone County: 25.7 %Boone County25.7Grundy County: 25.6 %Grundy County25.6Will County: 25.5 %Will County25.5Douglas County: 25.3 %Douglas County25.3Moultrie County: 25.3 %Moultrie County25.3Cass County: 24.7 %Cass County24.7Woodford County: 24.7 %Woodford County24.7Lake County: 24.6 %Lake County24.6McHenry County: 23.8 %McHenry County23.8St. Clair County: 23.8 %St. Clair County23.8Peoria County: 23.5 %Peoria County23.5Vermilion County: 23.4 %Vermilion County23.4Kankakee County: 23.3 %Kankakee County23.3Winnebago County: 23.3 %Winnebago County23.3Effingham County: 23.2 %Effingham County23.2Wayne County: 23.2 %Wayne County23.2Tazewell County: 23 %Tazewell County23Massac County: 23 %Massac County23Alexander County: 23 %Alexander County23Henry County: 23 %Henry County23Ford County: 23 %Ford County23Ogle County: 23 %Ogle County23DuPage County: 22.8 %DuPage County22.8Clark County: 22.8 %Clark County22.8Marion County: 22.8 %Marion County22.8Monroe County: 22.8 %Monroe County22.8Menard County: 22.8 %Menard County22.8Hamilton County: 22.7 %Hamilton County22.7Edwards County: 22.7 %Edwards County22.7Cumberland County: 22.6 %Cumberland County22.6Richland County: 22.6 %Richland County22.6Clay County: 22.5 %Clay County22.5Jasper County: 22.5 %Jasper County22.5Piatt County: 22.5 %Piatt County22.5Adams County: 22.4 %Adams County22.4Sangamon County: 22.4 %Sangamon County22.4DeKalb County: 22.4 %DeKalb County22.4Pike County: 22.4 %Pike County22.4
%. Source: Invokely calculation with data from U.S. Census Bureau. Retrieved 2026-10-12.

Full ranking

RankCounties2017 (%)Change on 2016
1Kendall County29.5-0.4 pts
2Kane County26-0.4 pts
3Boone County25.7-0.3 pts
4Grundy County25.6-0.1 pts
5Will County25.5-0.4 pts
6Douglas County25.3-0 pts
7Moultrie County25.3+0.3 pts
8Cass County24.7+0.3 pts
9Woodford County24.7-0.2 pts
10Lake County24.6-0.3 pts
11McHenry County23.8-0.3 pts
12St. Clair County23.8-0.1 pts
13Peoria County23.5-0.1 pts
14Vermilion County23.4-0.2 pts
15Kankakee County23.3-0.3 pts
16Winnebago County23.3-0.2 pts
17Effingham County23.2-0.1 pts
18Wayne County23.2-0 pts
19Tazewell County23-0.1 pts
20Massac County23+0.1 pts
21Alexander County23+0.6 pts
22Henry County23-0 pts
23Ford County23-0.1 pts
24Ogle County23-0.2 pts
25DuPage County22.8-0.2 pts
26Clark County22.8-0.1 pts
27Marion County22.8+0.1 pts
28Monroe County22.8-0.4 pts
29Menard County22.8+0.3 pts
30Hamilton County22.7-0 pts
31Edwards County22.7-0.1 pts
32Cumberland County22.6-0 pts
33Richland County22.6+0.2 pts
34Clay County22.5-0 pts
35Jasper County22.5-0.1 pts
36Piatt County22.5-0.1 pts
37Adams County22.4-0.2 pts
38Sangamon County22.4-0.2 pts
39DeKalb County22.40 pts
40Pike County22.4-0.3 pts
41Saline County22.4-0 pts
42Jefferson County22.30 pts
43Macon County22.2-0.1 pts
44Rock Island County22.2-0.1 pts
45Pulaski County22.1+0.2 pts
46Iroquois County22.1-0.1 pts
47Whiteside County22.1-0.2 pts
48McLean County22.1-0.1 pts
49Franklin County22+0.1 pts
50Scott County22+0.1 pts
51Stark County22-0.5 pts
52Williamson County21.9-0.1 pts
53Livingston County21.9-0 pts
54Greene County21.9+0.1 pts
55Mercer County21.90 pts
56Wabash County21.8-0.4 pts
57De Witt County21.8-0.3 pts
58Madison County21.8-0.1 pts
59Warren County21.7-0.4 pts
60Bureau County21.7-0.1 pts
61Clinton County21.7-0 pts
62Cook County21.7-0.3 pts
63LaSalle County21.5-0.2 pts
64Stephenson County21.5-0.2 pts
65White County21.30 pts
66Washington County21.3-0.1 pts
67Hancock County21.2-0.2 pts
68Macoupin County21.2-0.1 pts
69Shelby County21.2-0.1 pts
70Fayette County21.1-0.1 pts
71Edgar County21-0 pts
72Gallatin County21-0.2 pts
73Calhoun County20.9-0 pts
74Jersey County20.8-0.3 pts
75Union County20.5-0.1 pts
76Montgomery County20.5+0.1 pts
77Marshall County20.4-0.2 pts
78Mason County20.4-0.1 pts
79Christian County20.4-0.1 pts
80Fulton County20.1-0.2 pts
81Crawford County20.1-0.2 pts
82Lee County20.1+0.2 pts
83Randolph County20+0.3 pts
84Putnam County20+0.8 pts
85Morgan County19.9-0 pts
86Knox County19.9+0.1 pts
87Logan County19.6-0 pts
88Perry County19.5-0.1 pts
89Jo Daviess County19.50 pts
90Coles County19.3+0.2 pts
91Champaign County19.3+0.2 pts
92Lawrence County19.2-0.1 pts
93Schuyler County19.1-0 pts
94Jackson County19+0.3 pts
95Henderson County19+0.1 pts
96Bond County18.7-0.2 pts
97Carroll County18.3-0.3 pts
98Hardin County18.1-0.9 pts
99McDonough County18+0.3 pts
100Johnson County17.9-0.2 pts
101Pope County17.7+0.1 pts
102Brown County16.5+0.4 pts

Other periods

About this ranking

Residents aged 0 to 17 as a percentage of total population on 1 July. United States: Census Bureau county population estimates by age; states and the nation are sums of their counties.

Uses the US age of majority. Not comparable with population_0_14_share, which stops at 14.

Every value in the ranking comes from the same publisher and the same period, so the counties are compared on one definition. Equal values share a rank.

How to cite

U.S. Census Bureau. Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties. https://www.census.gov/programs-surveys/popest/data/data-sets.html. Retrieved 2026-10-12.

Citation styles

The publisher is the author. Invokely is named only as the place the figures were read, where a style asks for it.

APA 7

U.S. Census Bureau. (2026). Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties (Counties in Illinois by population under 18, 2017) [Data set]. Retrieved October 12, 2026, from https://www.census.gov/programs-surveys/popest/data/data-sets.html

MLA 9

Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties, Counties in Illinois by population under 18, 2017. U.S. Census Bureau, 25 June 2026, https://www.census.gov/programs-surveys/popest/data/data-sets.html. Invokely, https://invokely.ai/rankings/population-under-18/illinois-counties?period=2017. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Census Bureau. 2026. Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties. Counties in Illinois by population under 18, 2017. Dataset. Accessed October 12, 2026. https://www.census.gov/programs-surveys/popest/data/data-sets.html. Also distributed by Invokely, https://invokely.ai/rankings/population-under-18/illinois-counties?period=2017.

Harvard

U.S. Census Bureau (2026) Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties, Counties in Illinois by population under 18, 2017 [Dataset]. Available at: https://www.census.gov/programs-surveys/popest/data/data-sets.html, via Invokely: https://invokely.ai/rankings/population-under-18/illinois-counties?period=2017 (Accessed: 12 October 2026).

BibTeX
@misc{census_counties_in_illinois_by_2017,
  author = {{U.S. Census Bureau}},
  title = {{Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties: Counties in Illinois by population under 18, 2017}},
  year = {2026},
  howpublished = {Data set},
  url = {https://www.census.gov/programs-surveys/popest/data/data-sets.html},
  urldate = {2026-10-12},
  note = {Accessed via Invokely, https://invokely.ai/rankings/population-under-18/illinois-counties?period=2017. Publisher attribution: U.S. Census Bureau. Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties. https://www.census.gov/programs-surveys/popest/data/data-sets.html. Retrieved 2026-10-12.},
}
RIS
TY  - DATA
AU  - U.S. Census Bureau
TI  - Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties: Counties in Illinois by population under 18, 2017
PY  - 2026
DA  - 2026/06/25
PB  - U.S. Census Bureau
DB  - Invokely
UR  - https://www.census.gov/programs-surveys/popest/data/data-sets.html
L2  - https://invokely.ai/rankings/population-under-18/illinois-counties?period=2017
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/population-under-18/illinois-counties?period=2017.
N1  - Publisher attribution: U.S. Census Bureau. Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties. https://www.census.gov/programs-surveys/popest/data/data-sets.html. Retrieved 2026-10-12.
ER  -
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Rank Counties in Illinois by population under 18 using official data, and cite the source.
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Questions

Which county has the highest population under 18?

Kendall County, with 29.5% in 2017, according to the U.S. Census Bureau.

Which county has the lowest population under 18?

Brown County, with 16.5% in 2017.

Where does this ranking come from?

Every value comes from one source and one period, so the places are comparable: U.S. Census Bureau, Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties. Retrieved 2026-10-12.

Population under 18: other rankings

Counties in Illinois: more rankings