Data / Rankings / Population under 18 / Counties in Illinois

Counties in Illinois by population under 18, 2025

Kendall County had the highest population under 18 of 102 counties in 2025, at 25.7%. Pope County had the lowest, at 13.9%. The median was 20.9% and the figure for Illinois was 20.6%. Source: the U.S. Census Bureau.

Highest25.7Kendall County
Lowest13.9Pope County
Median20.9102 counties
Illinois20.6History

Top 40 counties, 2025

Kendall County: 25.7 %Kendall County25.7Douglas County: 24.5 %Douglas County24.5Moultrie County: 23.7 %Moultrie County23.7Cass County: 23.6 %Cass County23.6Woodford County: 23.3 %Woodford County23.3Peoria County: 23 %Peoria County23Jasper County: 23 %Jasper County23Pike County: 22.8 %Pike County22.8Grundy County: 22.7 %Grundy County22.7Effingham County: 22.7 %Effingham County22.7Vermilion County: 22.7 %Vermilion County22.7Wayne County: 22.6 %Wayne County22.6Kane County: 22.6 %Kane County22.6Boone County: 22.5 %Boone County22.5Ford County: 22.5 %Ford County22.5Marion County: 22.4 %Marion County22.4Clay County: 22.4 %Clay County22.4Winnebago County: 22.4 %Winnebago County22.4Will County: 22.3 %Will County22.3Stark County: 22.3 %Stark County22.3Rock Island County: 22.1 %Rock Island County22.1Cumberland County: 22 %Cumberland County22Macon County: 22 %Macon County22Jefferson County: 21.9 %Jefferson County21.9Piatt County: 21.9 %Piatt County21.9St. Clair County: 21.9 %St. Clair County21.9Lake County: 21.8 %Lake County21.8Hamilton County: 21.8 %Hamilton County21.8Clark County: 21.8 %Clark County21.8Kankakee County: 21.7 %Kankakee County21.7Greene County: 21.6 %Greene County21.6Adams County: 21.6 %Adams County21.6Ogle County: 21.6 %Ogle County21.6Warren County: 21.6 %Warren County21.6McHenry County: 21.5 %McHenry County21.5Clinton County: 21.4 %Clinton County21.4Henry County: 21.4 %Henry County21.4Richland County: 21.3 %Richland County21.3Livingston County: 21.3 %Livingston County21.3Franklin County: 21.2 %Franklin County21.2
%. Source: Invokely calculation with data from U.S. Census Bureau. Retrieved 2026-10-12.

Full ranking

RankCounties2025 (%)Change on 2024
1Kendall County25.7-0.7 pts
2Douglas County24.5-0.1 pts
3Moultrie County23.7-0.2 pts
4Cass County23.6-0.2 pts
5Woodford County23.3-0.1 pts
6Peoria County23-0.2 pts
7Jasper County23+0.1 pts
8Pike County22.8-0.4 pts
9Grundy County22.7-0.5 pts
10Effingham County22.7-0.3 pts
11Vermilion County22.7-0.1 pts
12Wayne County22.6-0.2 pts
13Kane County22.6-0.4 pts
14Boone County22.5-0.4 pts
15Ford County22.50 pts
16Marion County22.4-0.2 pts
17Clay County22.4-0 pts
18Winnebago County22.4-0.2 pts
19Will County22.3-0.4 pts
20Stark County22.3+0.3 pts
21Rock Island County22.1+0.1 pts
22Cumberland County22-0.2 pts
23Macon County22-0.2 pts
24Jefferson County21.9+0.1 pts
25Piatt County21.9-0 pts
26St. Clair County21.9-0.5 pts
27Lake County21.8-0.4 pts
28Hamilton County21.8-0.2 pts
29Clark County21.8-0.1 pts
30Kankakee County21.7-0.4 pts
31Greene County21.60 pts
32Adams County21.6-0.1 pts
33Ogle County21.6-0.1 pts
34Warren County21.6-0.2 pts
35McHenry County21.5-0.3 pts
36Clinton County21.4-0.2 pts
37Henry County21.4-0.1 pts
38Richland County21.3-0.2 pts
39Livingston County21.3-0.2 pts
40Franklin County21.2-0.2 pts
41Shelby County21.2-0 pts
42DuPage County21.2-0.2 pts
43Whiteside County21.2-0.3 pts
44Menard County21.2-0.5 pts
45DeKalb County21.2-0.2 pts
46Monroe County21.1-0.7 pts
47Iroquois County21.1-0.1 pts
48Tazewell County21.1-0.3 pts
49Sangamon County21-0.2 pts
50Wabash County20.9-0.2 pts
51Mercer County20.90 pts
52Edwards County20.9-0.3 pts
53Saline County20.7-0.3 pts
54Fayette County20.7+0.1 pts
55De Witt County20.7-0.4 pts
56Hancock County20.6-0.1 pts
57Madison County20.5-0.3 pts
58Stephenson County20.5-0.2 pts
59Edgar County20.3-0.1 pts
60Williamson County20.3-0.2 pts
61LaSalle County20.3-0.3 pts
62White County20.2-0.5 pts
63Marshall County20.2-0.3 pts
64Union County20.1-0.2 pts
65McLean County20.1-0.3 pts
66Washington County20.1-0.2 pts
67Massac County20.1-0.4 pts
68Pulaski County20.1-0.4 pts
69Bureau County19.9-0.1 pts
70Macoupin County19.8-0.3 pts
71Mason County19.8+0.1 pts
72Calhoun County19.70 pts
73Hardin County19.6+0.5 pts
74Crawford County19.60 pts
75Knox County19.6-0.2 pts
76Randolph County19.4-0.3 pts
77Lawrence County19.4-0.4 pts
78Cook County19.4-0.4 pts
79Scott County19.4-0.6 pts
80Montgomery County19.3-0.3 pts
81Jackson County19.2-0.2 pts
82Coles County19.20 pts
83McDonough County19.2+0.1 pts
84Jersey County19.1-0.5 pts
85Morgan County19-0.2 pts
86Logan County18.9-0.2 pts
87Lee County18.8-0.3 pts
88Henderson County18.8-0.1 pts
89Fulton County18.7-0.1 pts
90Christian County18.7-0.2 pts
91Putnam County18.5-0 pts
92Champaign County18.5-0.2 pts
93Alexander County18.3-0.5 pts
94Perry County18.2-0.2 pts
95Gallatin County17.9-0.7 pts
96Jo Daviess County17.7-0.2 pts
97Carroll County17.40 pts
98Schuyler County17-0.5 pts
99Bond County16.9-0.6 pts
100Johnson County16.6+0.1 pts
101Brown County16.2-0 pts
102Pope County13.9-1.2 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.

Use this data in your AI agent

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Rank Counties in Illinois by population under 18 using official data, and cite the source.
rank_places {"indicator":"population_0_17_share","level":"province","within":"Illinois","limit":10}
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Questions

Which county has the highest population under 18?

Kendall County, with 25.7% in 2025, according to the U.S. Census Bureau.

Which county has the lowest population under 18?

Pope County, with 13.9% in 2025.

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