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 2016, at 29.8%. Brown County had the lowest, at 16.1%. The median was 22.1% and the figure for Illinois was 22.8%. Source: the U.S. Census Bureau.

Highest29.8Kendall County
Lowest16.1Brown County
Median22.1102 counties
Illinois22.8History

Top 40 counties, 2016

Kendall County: 29.8 %Kendall County29.8Kane County: 26.4 %Kane County26.4Boone County: 26 %Boone County26Will County: 25.9 %Will County25.9Grundy County: 25.7 %Grundy County25.7Douglas County: 25.4 %Douglas County25.4Moultrie County: 24.9 %Moultrie County24.9Lake County: 24.9 %Lake County24.9Woodford County: 24.8 %Woodford County24.8Cass County: 24.5 %Cass County24.5McHenry County: 24.2 %McHenry County24.2St. Clair County: 23.9 %St. Clair County23.9Kankakee County: 23.6 %Kankakee County23.6Vermilion County: 23.6 %Vermilion County23.6Peoria County: 23.6 %Peoria County23.6Winnebago County: 23.4 %Winnebago County23.4Effingham County: 23.4 %Effingham County23.4Wayne County: 23.2 %Wayne County23.2Ogle County: 23.2 %Ogle County23.2Monroe County: 23.2 %Monroe County23.2Tazewell County: 23.1 %Tazewell County23.1Henry County: 23 %Henry County23Ford County: 23 %Ford County23DuPage County: 23 %DuPage County23Massac County: 23 %Massac County23Clark County: 22.9 %Clark County22.9Edwards County: 22.8 %Edwards County22.8Hamilton County: 22.7 %Hamilton County22.7Marion County: 22.7 %Marion County22.7Pike County: 22.6 %Pike County22.6Cumberland County: 22.6 %Cumberland County22.6Adams County: 22.6 %Adams County22.6Sangamon County: 22.6 %Sangamon County22.6Piatt County: 22.6 %Piatt County22.6Jasper County: 22.6 %Jasper County22.6Clay County: 22.5 %Clay County22.5Menard County: 22.5 %Menard County22.5Richland County: 22.4 %Richland County22.4Alexander County: 22.4 %Alexander County22.4Stark County: 22.4 %Stark County22.4
%. Source: Invokely calculation with data from U.S. Census Bureau. Retrieved 2026-10-12.

Full ranking

RankCounties2016 (%)Change on 2015
1Kendall County29.8-0.2 pts
2Kane County26.4-0.4 pts
3Boone County26-0.2 pts
4Will County25.9-0.4 pts
5Grundy County25.7-0.2 pts
6Douglas County25.40 pts
7Moultrie County24.9+0.2 pts
8Lake County24.9-0.3 pts
9Woodford County24.8-0.1 pts
10Cass County24.5+0.3 pts
11McHenry County24.2-0.4 pts
12St. Clair County23.9-0 pts
13Kankakee County23.6-0.2 pts
14Vermilion County23.6-0 pts
15Peoria County23.6-0.1 pts
16Winnebago County23.4-0.2 pts
17Effingham County23.4-0.2 pts
18Wayne County23.2+0.2 pts
19Ogle County23.2-0 pts
20Monroe County23.2-0.1 pts
21Tazewell County23.1-0.1 pts
22Henry County230 pts
23Ford County23-0.1 pts
24DuPage County23-0.2 pts
25Massac County23+0.3 pts
26Clark County22.9+0.2 pts
27Edwards County22.8+0.3 pts
28Hamilton County22.7+0.5 pts
29Marion County22.7-0.2 pts
30Pike County22.6+0.2 pts
31Cumberland County22.6-0.1 pts
32Adams County22.6-0 pts
33Sangamon County22.6-0.1 pts
34Piatt County22.6+0.2 pts
35Jasper County22.6-0.1 pts
36Clay County22.5+0.1 pts
37Menard County22.5+0.3 pts
38Richland County22.4+0.1 pts
39Alexander County22.4-0.9 pts
40Stark County22.4+0.2 pts
41Saline County22.4-0.1 pts
42DeKalb County22.4-0 pts
43Macon County22.30 pts
44Whiteside County22.3-0.2 pts
45Jefferson County22.2+0.2 pts
46Rock Island County22.2-0.2 pts
47Wabash County22.2+0.2 pts
48Iroquois County22.2-0.1 pts
49De Witt County22.2+0.1 pts
50McLean County22.1-0 pts
51Warren County22.1+0.2 pts
52Williamson County22.10 pts
53Livingston County220 pts
54Pulaski County21.9+0.5 pts
55Cook County21.9-0.2 pts
56Bureau County21.9+0.1 pts
57Franklin County21.9-0.2 pts
58Scott County21.9-0.5 pts
59Madison County21.8-0.2 pts
60Mercer County21.8-0.2 pts
61Greene County21.8-0.2 pts
62Stephenson County21.8+0.1 pts
63Clinton County21.7-0 pts
64LaSalle County21.7-0.1 pts
65Hancock County21.4+0.2 pts
66Washington County21.3+0.3 pts
67Macoupin County21.3-0 pts
68White County21.3-0.3 pts
69Shelby County21.30 pts
70Gallatin County21.2+0.4 pts
71Fayette County21.1-0.1 pts
72Jersey County21.1-0.2 pts
73Edgar County21-0.3 pts
74Calhoun County20.9+0.2 pts
75Marshall County20.6+0.4 pts
76Union County20.6-0.1 pts
77Christian County20.5-0.3 pts
78Mason County20.5-0.2 pts
79Montgomery County20.4-0.1 pts
80Crawford County20.3-0.1 pts
81Fulton County20.3+0.1 pts
82Morgan County19.9-0.4 pts
83Lee County19.9-0.2 pts
84Knox County19.8-0 pts
85Randolph County19.7+0.2 pts
86Perry County19.7+0.2 pts
87Logan County19.6+0.1 pts
88Jo Daviess County19.5-0.1 pts
89Lawrence County19.3+0.1 pts
90Putnam County19.2-0.4 pts
91Coles County19.2+0.2 pts
92Schuyler County19.2-0.6 pts
93Champaign County19.1-0 pts
94Hardin County19.1-0.3 pts
95Bond County18.9-0 pts
96Henderson County18.9-0.4 pts
97Jackson County18.7+0.3 pts
98Carroll County18.6+0.1 pts
99Johnson County18.1+0.4 pts
100McDonough County17.7+0.5 pts
101Pope County17.6+0.2 pts
102Brown County16.1+0.1 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, 2016) [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, 2016. 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=2016. 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, 2016. 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=2016.

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, 2016 [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=2016 (Accessed: 12 October 2026).

BibTeX
@misc{census_counties_in_illinois_by_2016,
  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, 2016}},
  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=2016. 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, 2016
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=2016
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/population-under-18/illinois-counties?period=2016.
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 29.8% in 2016, according to the U.S. Census Bureau.

Which county has the lowest population under 18?

Brown County, with 16.1% in 2016.

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