Data / Rankings / Population under 18 / Counties in Montana

Counties in Montana by population under 18

Big Horn County had the highest population under 18 of 56 counties in 2015, at 33.3%. Powell County had the lowest, at 15.6%. The median was 21.3% and the figure for Montana was 22.1%. Source: the U.S. Census Bureau.

Highest33.3Big Horn County
Lowest15.6Powell County
Median21.356 counties
Montana22.1History

All counties, 2015

Big Horn County: 33.3 %Big Horn County33.3Roosevelt County: 31.3 %Roosevelt County31.3Glacier County: 31.1 %Glacier County31.1Blaine County: 29.7 %Blaine County29.7Rosebud County: 28.4 %Rosebud County28.4Fallon County: 26.9 %Fallon County26.9Hill County: 26.7 %Hill County26.7Chouteau County: 25.7 %Chouteau County25.7Richland County: 25.4 %Richland County25.4Lake County: 24.6 %Lake County24.6Pondera County: 24.4 %Pondera County24.4Liberty County: 24 %Liberty County24Garfield County: 24 %Garfield County24Yellowstone County: 23.7 %Yellowstone County23.7Wibaux County: 23.4 %Wibaux County23.4Phillips County: 23.3 %Phillips County23.3Custer County: 23.1 %Custer County23.1Dawson County: 22.9 %Dawson County22.9Teton County: 22.9 %Teton County22.9Valley County: 22.8 %Valley County22.8Flathead County: 22.6 %Flathead County22.6Sweet Grass County: 22.5 %Sweet Grass County22.5Cascade County: 22.4 %Cascade County22.4Lewis and Clark County: 21.8 %Lewis and Clark County21.8Broadwater County: 21.5 %Broadwater County21.5Stillwater County: 21.4 %Stillwater County21.4Wheatland County: 21.4 %Wheatland County21.4Sheridan County: 21.3 %Sheridan County21.3Daniels County: 21.3 %Daniels County21.3Jefferson County: 20.9 %Jefferson County20.9Fergus County: 20.8 %Fergus County20.8Musselshell County: 20.6 %Musselshell County20.6Gallatin County: 20.6 %Gallatin County20.6Ravalli County: 20.3 %Ravalli County20.3Silver Bow County: 20.3 %Silver Bow County20.3Missoula County: 19.9 %Missoula County19.9McCone County: 19.8 %McCone County19.8Granite County: 19.4 %Granite County19.4Beaverhead County: 19.3 %Beaverhead County19.3Carter County: 19.1 %Carter County19.1Park County: 18.9 %Park County18.9Toole County: 18.9 %Toole County18.9Powder River County: 18.8 %Powder River County18.8Golden Valley County: 18.8 %Golden Valley County18.8Carbon County: 18.6 %Carbon County18.6Lincoln County: 18.6 %Lincoln County18.6Petroleum County: 18.5 %Petroleum County18.5Sanders County: 18.3 %Sanders County18.3Mineral County: 17.9 %Mineral County17.9Prairie County: 17.9 %Prairie County17.9Treasure County: 17.9 %Treasure County17.9Judith Basin County: 17.8 %Judith Basin County17.8Deer Lodge County: 17.5 %Deer Lodge County17.5Meagher County: 17.1 %Meagher County17.1Madison County: 16.3 %Madison County16.3Powell County: 15.6 %Powell County15.6
%. Source: Invokely calculation with data from U.S. Census Bureau. Retrieved 2026-10-12.

Full ranking

RankCounties2015 (%)Change on 2014
1Big Horn County33.3-0.2 pts
2Roosevelt County31.3+0.2 pts
3Glacier County31.1-0.1 pts
4Blaine County29.7+0.1 pts
5Rosebud County28.4-0.2 pts
6Fallon County26.9+1.1 pts
7Hill County26.7+0.2 pts
8Chouteau County25.7-0.5 pts
9Richland County25.4+0.8 pts
10Lake County24.6-0.1 pts
11Pondera County24.4-0.6 pts
12Liberty County24+1.2 pts
13Garfield County24+0.1 pts
14Yellowstone County23.7-0 pts
15Wibaux County23.4+0.7 pts
16Phillips County23.3+0.8 pts
17Custer County23.1+0.3 pts
18Dawson County22.9+0.4 pts
19Teton County22.9+0.1 pts
20Valley County22.8-0.2 pts
21Flathead County22.6-0.2 pts
22Sweet Grass County22.5-0.4 pts
23Cascade County22.4-0 pts
24Lewis and Clark County21.8-0.2 pts
25Broadwater County21.5+0.2 pts
26Stillwater County21.4-0.2 pts
27Wheatland County21.4-0.7 pts
28Sheridan County21.3+0.7 pts
29Daniels County21.3-0.4 pts
30Jefferson County20.9-0.4 pts
31Fergus County20.8+0.4 pts
32Musselshell County20.6+0.7 pts
33Gallatin County20.6-0.2 pts
34Ravalli County20.3-0.3 pts
35Silver Bow County20.3-0.2 pts
36Missoula County19.9+0.1 pts
37McCone County19.8-0.7 pts
38Granite County19.4+1.1 pts
39Beaverhead County19.3+0.3 pts
40Carter County19.1+0.7 pts
41Park County18.9-0.1 pts
42Toole County18.9-0.4 pts
43Powder River County18.8+0.4 pts
44Golden Valley County18.8-1 pts
45Carbon County18.6-0.3 pts
45Lincoln County18.60 pts
47Petroleum County18.5-3 pts
48Sanders County18.3-0.3 pts
49Mineral County17.9-0.6 pts
50Prairie County17.9+0.4 pts
51Treasure County17.9-0.6 pts
52Judith Basin County17.8-0.5 pts
53Deer Lodge County17.50 pts
54Meagher County17.1-0.9 pts
55Madison County16.30 pts
56Powell County15.6-0.2 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.

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, 2015) [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, 2015. 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=2015. 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, 2015. 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=2015.

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, 2015 [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=2015 (Accessed: 12 October 2026).

BibTeX
@misc{census_counties_in_montana_by_2015,
  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, 2015}},
  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=2015. 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, 2015
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=2015
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/population-under-18/montana-counties?period=2015.
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?

Big Horn County, with 33.3% in 2015, according to the U.S. Census Bureau.

Which county has the lowest population under 18?

Powell County, with 15.6% in 2015.

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