Data / Rankings / Population under 18 / Counties in Montana

Counties in Montana by population under 18

Roosevelt County had the highest population under 18 of 56 counties in 2024, at 31.5%. Deer Lodge County had the lowest, at 14.7%. The median was 20.9% and the figure for Montana was 20.5%. Source: the U.S. Census Bureau.

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Highest31.5Roosevelt County
Lowest14.7Deer Lodge County
Median20.956 counties
Montana20.5History

Map of counties, 2024

Beaverhead County: 17.5 %Big Horn County: 30.8 %Blaine County: 26.9 %Broadwater County: 21.3 %Carbon County: 17.8 %Carter County: 21.9 %Cascade County: 21.4 %Chouteau County: 22.1 %Custer County: 21.1 %Daniels County: 21.1 %Dawson County: 21.2 %Deer Lodge County: 14.7 %Fallon County: 25.4 %Fergus County: 20.8 %Flathead County: 21.5 %Gallatin County: 18.2 %Garfield County: 24.9 %Glacier County: 28.8 %Golden Valley County: 19.1 %Granite County: 16 %Hill County: 26.9 %Jefferson County: 20.3 %Judith Basin County: 18.3 %Lake County: 21.1 %Lewis and Clark County: 20.7 %Liberty County: 24.9 %Lincoln County: 18.1 %McCone County: 20.7 %Madison County: 15.7 %Meagher County: 16.8 %Mineral County: 17.7 %Missoula County: 18 %Musselshell County: 21.1 %Park County: 16.6 %Petroleum County: 15.8 %Phillips County: 23.2 %Pondera County: 23.2 %Powder River County: 20.3 %Powell County: 15.1 %Prairie County: 20.3 %Ravalli County: 18.6 %Richland County: 23.8 %Roosevelt County: 31.5 %Rosebud County: 27.7 %Sanders County: 16.8 %Sheridan County: 20.3 %Silver Bow County: 19.1 %Stillwater County: 20.6 %Sweet Grass County: 18.1 %Teton County: 23.7 %Toole County: 20.5 %Treasure County: 23.8 %Valley County: 21.8 %Wheatland County: 21 %Wibaux County: 21.9 %Yellowstone County: 22.1 %
  • Under 18
  • 18 to 19
  • 19 to 21
  • 21 to 22
  • 22 to 24
  • 24 and over
%, 2024. Source: Invokely calculation with data from U.S. Census Bureau. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2024

Roosevelt County: 31.5 %Roosevelt County31.5Big Horn County: 30.8 %Big Horn County30.8Glacier County: 28.8 %Glacier County28.8Rosebud County: 27.7 %Rosebud County27.7Hill County: 26.9 %Hill County26.9Blaine County: 26.9 %Blaine County26.9Fallon County: 25.4 %Fallon County25.4Garfield County: 24.9 %Garfield County24.9Liberty County: 24.9 %Liberty County24.9Richland County: 23.8 %Richland County23.8Treasure County: 23.8 %Treasure County23.8Teton County: 23.7 %Teton County23.7Phillips County: 23.2 %Phillips County23.2Pondera County: 23.2 %Pondera County23.2Yellowstone County: 22.1 %Yellowstone County22.1Chouteau County: 22.1 %Chouteau County22.1Carter County: 21.9 %Carter County21.9Wibaux County: 21.9 %Wibaux County21.9Valley County: 21.8 %Valley County21.8Flathead County: 21.5 %Flathead County21.5Cascade County: 21.4 %Cascade County21.4Broadwater County: 21.3 %Broadwater County21.3Dawson County: 21.2 %Dawson County21.2Lake County: 21.1 %Lake County21.1Custer County: 21.1 %Custer County21.1Daniels County: 21.1 %Daniels County21.1Musselshell County: 21.1 %Musselshell County21.1Wheatland County: 21 %Wheatland County21Fergus County: 20.8 %Fergus County20.8McCone County: 20.7 %McCone County20.7Lewis and Clark County: 20.7 %Lewis and Clark County20.7Stillwater County: 20.6 %Stillwater County20.6Toole County: 20.5 %Toole County20.5Sheridan County: 20.3 %Sheridan County20.3Powder River County: 20.3 %Powder River County20.3Prairie County: 20.3 %Prairie County20.3Jefferson County: 20.3 %Jefferson County20.3Silver Bow County: 19.1 %Silver Bow County19.1Golden Valley County: 19.1 %Golden Valley County19.1Ravalli County: 18.6 %Ravalli County18.6Judith Basin County: 18.3 %Judith Basin County18.3Gallatin County: 18.2 %Gallatin County18.2Lincoln County: 18.1 %Lincoln County18.1Sweet Grass County: 18.1 %Sweet Grass County18.1Missoula County: 18 %Missoula County18Carbon County: 17.8 %Carbon County17.8Mineral County: 17.7 %Mineral County17.7Beaverhead County: 17.5 %Beaverhead County17.5Sanders County: 16.8 %Sanders County16.8Meagher County: 16.8 %Meagher County16.8Park County: 16.6 %Park County16.6Granite County: 16 %Granite County16Petroleum County: 15.8 %Petroleum County15.8Madison County: 15.7 %Madison County15.7Powell County: 15.1 %Powell County15.1Deer Lodge County: 14.7 %Deer Lodge County14.7Roosevelt County: 31.5 %Roosevelt County31.5Big Horn County: 30.8 %Big Horn County30.8Glacier County: 28.8 %Glacier County28.8Rosebud County: 27.7 %Rosebud County27.7Hill County: 26.9 %Hill County26.9Blaine County: 26.9 %Blaine County26.9Fallon County: 25.4 %Fallon County25.4Garfield County: 24.9 %Garfield County24.9Liberty County: 24.9 %Liberty County24.9Richland County: 23.8 %Richland County23.8Treasure County: 23.8 %Treasure County23.8Teton County: 23.7 %Teton County23.7Phillips County: 23.2 %Phillips County23.2Pondera County: 23.2 %Pondera County23.2Yellowstone County: 22.1 %Yellowstone County22.1Chouteau County: 22.1 %Chouteau County22.1Carter County: 21.9 %Carter County21.9Wibaux County: 21.9 %Wibaux County21.9Valley County: 21.8 %Valley County21.8Flathead County: 21.5 %Flathead County21.5Cascade County: 21.4 %Cascade County21.4Broadwater County: 21.3 %Broadwater County21.3Dawson County: 21.2 %Dawson County21.2Lake County: 21.1 %Lake County21.1Custer County: 21.1 %Custer County21.1Daniels County: 21.1 %Daniels County21.1Musselshell County: 21.1 %Musselshell County21.1Wheatland County: 21 %Wheatland County21Fergus County: 20.8 %Fergus County20.8McCone County: 20.7 %McCone County20.7Lewis and Clark County: 20.7 %Lewis and Clark County20.7Stillwater County: 20.6 %Stillwater County20.6Toole County: 20.5 %Toole County20.5Sheridan County: 20.3 %Sheridan County20.3Powder River County: 20.3 %Powder River County20.3Prairie County: 20.3 %Prairie County20.3Jefferson County: 20.3 %Jefferson County20.3Silver Bow County: 19.1 %Silver Bow County19.1Golden Valley County: 19.1 %Golden Valley County19.1Ravalli County: 18.6 %Ravalli County18.6Judith Basin County: 18.3 %Judith Basin County18.3Gallatin County: 18.2 %Gallatin County18.2Lincoln County: 18.1 %Lincoln County18.1Sweet Grass County: 18.1 %Sweet Grass County18.1Missoula County: 18 %Missoula County18Carbon County: 17.8 %Carbon County17.8Mineral County: 17.7 %Mineral County17.7Beaverhead County: 17.5 %Beaverhead County17.5Sanders County: 16.8 %Sanders County16.8Meagher County: 16.8 %Meagher County16.8Park County: 16.6 %Park County16.6Granite County: 16 %Granite County16Petroleum County: 15.8 %Petroleum County15.8Madison County: 15.7 %Madison County15.7Powell County: 15.1 %Powell County15.1Deer Lodge County: 14.7 %Deer Lodge County14.7
%. Source: Invokely calculation with data from U.S. Census Bureau. Retrieved 2026-10-12.

Full ranking

RankCounties2024 (%)Change on 2023
1Roosevelt County31.5-0.4 pts
2Big Horn County30.8-0.4 pts
3Glacier County28.8-0.5 pts
4Rosebud County27.7-0.4 pts
5Hill County26.9-0.4 pts
6Blaine County26.9-0.2 pts
7Fallon County25.4-0.2 pts
8Garfield County24.9-0.1 pts
9Liberty County24.9-0.3 pts
10Richland County23.8-0.1 pts
11Treasure County23.8+0.6 pts
12Teton County23.7-0.2 pts
13Phillips County23.2-0.5 pts
14Pondera County23.2-0.9 pts
15Yellowstone County22.1-0.3 pts
16Chouteau County22.1-0.4 pts
17Carter County21.9+0.6 pts
18Wibaux County21.9+0.9 pts
19Valley County21.8-0.5 pts
20Flathead County21.5-0.3 pts
21Cascade County21.4-0.4 pts
22Broadwater County21.3+0.2 pts
23Dawson County21.2-0.1 pts
24Lake County21.1-0.4 pts
25Custer County21.1-0.4 pts
26Daniels County21.1+0.4 pts
27Musselshell County21.1+0.2 pts
28Wheatland County21+0.1 pts
29Fergus County20.8-0.1 pts
30McCone County20.7+0.6 pts
31Lewis and Clark County20.7-0.3 pts
32Stillwater County20.6+0.3 pts
33Toole County20.5+0.1 pts
34Sheridan County20.3-0.7 pts
35Powder River County20.3+0.6 pts
35Prairie County20.3+0.1 pts
37Jefferson County20.3-0.4 pts
38Silver Bow County19.1-0.4 pts
39Golden Valley County19.1-0 pts
40Ravalli County18.6-0.3 pts
41Judith Basin County18.3+0.4 pts
42Gallatin County18.2-0.3 pts
43Lincoln County18.1-0.3 pts
44Sweet Grass County18.1-0.5 pts
45Missoula County18-0.4 pts
46Carbon County17.8-0.2 pts
47Mineral County17.7-0.7 pts
48Beaverhead County17.5-0.5 pts
49Sanders County16.8-0 pts
50Meagher County16.8-0.1 pts
51Park County16.6-0.3 pts
52Granite County16-0.6 pts
53Petroleum County15.8+0.1 pts
54Madison County15.7-0.5 pts
55Powell County15.1+0.2 pts
56Deer Lodge County14.7+0.3 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 Montana by population under 18, 2024) [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 Montana by population under 18, 2024. 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/montana-counties?period=2024. 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 Montana by population under 18, 2024. 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/montana-counties?period=2024.

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 Montana by population under 18, 2024 [Dataset]. Available at: https://www.census.gov/programs-surveys/popest/data/data-sets.html, via Invokely: https://invokely.ai/rankings/population-under-18/montana-counties?period=2024 (Accessed: 12 October 2026).

BibTeX
@misc{census_counties_in_montana_by_2024,
  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 Montana by population under 18, 2024}},
  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/montana-counties?period=2024. 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 Montana by population under 18, 2024
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/montana-counties?period=2024
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/population-under-18/montana-counties?period=2024.
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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Questions

Which county has the highest population under 18?

Roosevelt County, with 31.5% in 2024, according to the U.S. Census Bureau.

Which county has the lowest population under 18?

Deer Lodge County, with 14.7% in 2024.

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 Montana: more rankings