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 2023, at 26.8%. Pope County had the lowest, at 15.5%. The median was 21.3% and the figure for Illinois was 21.2%. Source: the U.S. Census Bureau.

Highest26.8Kendall County
Lowest15.5Pope County
Median21.3102 counties
Illinois21.2History

Top 40 counties, 2023

Kendall County: 26.8 %Kendall County26.8Douglas County: 24.7 %Douglas County24.7Moultrie County: 24.1 %Moultrie County24.1Cass County: 23.9 %Cass County23.9Grundy County: 23.7 %Grundy County23.7Woodford County: 23.6 %Woodford County23.6Boone County: 23.5 %Boone County23.5Kane County: 23.4 %Kane County23.4Pike County: 23.4 %Pike County23.4Peoria County: 23.3 %Peoria County23.3Effingham County: 23.2 %Effingham County23.2Will County: 23.2 %Will County23.2Marion County: 23 %Marion County23Vermilion County: 22.8 %Vermilion County22.8Winnebago County: 22.8 %Winnebago County22.8St. Clair County: 22.8 %St. Clair County22.8Jasper County: 22.8 %Jasper County22.8Wayne County: 22.7 %Wayne County22.7Clay County: 22.7 %Clay County22.7Lake County: 22.7 %Lake County22.7Hamilton County: 22.6 %Hamilton County22.6Ford County: 22.6 %Ford County22.6Kankakee County: 22.3 %Kankakee County22.3McHenry County: 22.2 %McHenry County22.2Macon County: 22.2 %Macon County22.2Clark County: 22.1 %Clark County22.1Cumberland County: 22.1 %Cumberland County22.1Monroe County: 22.1 %Monroe County22.1Adams County: 22 %Adams County22Ogle County: 22 %Ogle County22Greene County: 22 %Greene County22Jefferson County: 22 %Jefferson County22Piatt County: 22 %Piatt County22Warren County: 22 %Warren County22Rock Island County: 22 %Rock Island County22Richland County: 21.9 %Richland County21.9Menard County: 21.9 %Menard County21.9Henry County: 21.8 %Henry County21.8Tazewell County: 21.7 %Tazewell County21.7DeKalb County: 21.7 %DeKalb County21.7
%. Source: Invokely calculation with data from U.S. Census Bureau. Retrieved 2026-10-12.

Full ranking

RankCounties2023 (%)Change on 2022
1Kendall County26.8-0.5 pts
2Douglas County24.7-0.1 pts
3Moultrie County24.1-0 pts
4Cass County23.9-0.2 pts
5Grundy County23.7-0.4 pts
6Woodford County23.6-0.2 pts
7Boone County23.5-0.3 pts
8Kane County23.4-0.5 pts
9Pike County23.4+0.1 pts
10Peoria County23.3+0.1 pts
11Effingham County23.2-0.1 pts
12Will County23.2-0.3 pts
13Marion County23-0.1 pts
14Vermilion County22.8-0.1 pts
15Winnebago County22.8-0.1 pts
16St. Clair County22.8-0.4 pts
17Jasper County22.8+0.1 pts
18Wayne County22.7+0.1 pts
19Clay County22.7-0.1 pts
20Lake County22.7-0.3 pts
21Hamilton County22.6-0.1 pts
22Ford County22.6-0.2 pts
23Kankakee County22.3-0.2 pts
24McHenry County22.2-0.3 pts
25Macon County22.2-0.1 pts
26Clark County22.1-0.2 pts
27Cumberland County22.1-0.3 pts
28Monroe County22.1-0.2 pts
29Adams County22-0.1 pts
30Ogle County22-0.2 pts
31Greene County22+0.3 pts
32Jefferson County22+0.1 pts
33Piatt County22+0.1 pts
34Warren County22-0.1 pts
35Rock Island County22-0.2 pts
36Richland County21.9-0.4 pts
37Menard County21.9+0.1 pts
38Henry County21.8-0.3 pts
39Tazewell County21.7-0.2 pts
40DeKalb County21.7-0.4 pts
41Stark County21.7+0.2 pts
42Clinton County21.7-0.1 pts
43Livingston County21.6-0 pts
44DuPage County21.6-0.2 pts
45Whiteside County21.50 pts
46Franklin County21.50 pts
47Wabash County21.5-0.3 pts
48Edwards County21.4-0.6 pts
49Sangamon County21.3-0.3 pts
50De Witt County21.3+0.2 pts
51Shelby County21.3-0 pts
52Iroquois County21.2-0.3 pts
53Saline County21.2-0.3 pts
54Hancock County21.1-0.1 pts
55White County21.1-0.2 pts
56Mercer County21.1-0 pts
57Massac County21.1-0.6 pts
58Madison County21-0.2 pts
59Williamson County20.9-0.3 pts
60Stephenson County20.9-0.1 pts
61LaSalle County20.80 pts
62McLean County20.7-0.4 pts
63Fayette County20.7-0.1 pts
64Washington County20.6-0.5 pts
65Edgar County20.6+0.1 pts
66Pulaski County20.4+0.2 pts
67Calhoun County20.4+0.1 pts
68Marshall County20.3-0.1 pts
69Macoupin County20.2-0.2 pts
70Bureau County20.2-0.3 pts
71Union County20.10 pts
72Lawrence County20.1-0.3 pts
73Montgomery County20.1-0.1 pts
74Cook County20-0.4 pts
75Knox County20+0.3 pts
76Randolph County19.9-0.1 pts
77Jersey County19.8-0.2 pts
78Alexander County19.8+0.1 pts
79Scott County19.7-0.2 pts
80Mason County19.6-0.4 pts
81Jackson County19.6-0.1 pts
82Crawford County19.5-0.5 pts
83Lee County19.5-0.4 pts
84Logan County19.3-0.2 pts
85Coles County19.3-0.1 pts
86Morgan County19.3+0.4 pts
87Hardin County19.1+0.7 pts
88Christian County19.1-0.3 pts
89Fulton County19-0.2 pts
90Gallatin County19-0.5 pts
91Putnam County18.9+0.5 pts
92Champaign County18.8-0.2 pts
93Henderson County18.8-0.1 pts
94McDonough County18.7+0.1 pts
95Perry County18.7-0.1 pts
96Jo Daviess County18-0.1 pts
97Bond County17.8-0.3 pts
98Carroll County17.7-0.1 pts
99Schuyler County17.5-0.4 pts
100Johnson County16.7-0.2 pts
101Brown County16.5-0.6 pts
102Pope County15.5-1.1 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, 2023) [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, 2023. 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=2023. 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, 2023. 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=2023.

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, 2023 [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=2023 (Accessed: 12 October 2026).

BibTeX
@misc{census_counties_in_illinois_by_2023,
  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, 2023}},
  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=2023. 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, 2023
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=2023
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/population-under-18/illinois-counties?period=2023.
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 26.8% in 2023, according to the U.S. Census Bureau.

Which county has the lowest population under 18?

Pope County, with 15.5% in 2023.

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