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 2017, at 34.2%. Powell County had the lowest, at 14.7%. The median was 21.2% and the figure for Montana was 22%. Source: the U.S. Census Bureau.

Keep it in a collection in your library.
Highest34.2Big Horn County
Lowest14.7Powell County
Median21.256 counties
Montana22History

Map of counties, 2017

Beaverhead County: 19.5 %Big Horn County: 34.2 %Blaine County: 29.5 %Broadwater County: 21.6 %Carbon County: 19 %Carter County: 21.4 %Cascade County: 22.4 %Chouteau County: 25.7 %Custer County: 22.8 %Daniels County: 21.7 %Dawson County: 22.5 %Deer Lodge County: 17 %Fallon County: 27.2 %Fergus County: 20.9 %Flathead County: 22.3 %Gallatin County: 20.3 %Garfield County: 24.1 %Glacier County: 31.2 %Golden Valley County: 20.4 %Granite County: 18.4 %Hill County: 26.7 %Jefferson County: 20.9 %Judith Basin County: 18.2 %Lake County: 24.1 %Lewis and Clark County: 21.6 %Liberty County: 23.7 %Lincoln County: 18.6 %McCone County: 21.1 %Madison County: 16.2 %Meagher County: 17 %Mineral County: 18.5 %Missoula County: 19.9 %Musselshell County: 19.6 %Park County: 18.1 %Petroleum County: 19.3 %Phillips County: 23.7 %Pondera County: 24.6 %Powder River County: 18.8 %Powell County: 14.7 %Prairie County: 17.7 %Ravalli County: 20 %Richland County: 24.5 %Roosevelt County: 31.8 %Rosebud County: 27.8 %Sanders County: 18.2 %Sheridan County: 20.5 %Silver Bow County: 20 %Stillwater County: 21.1 %Sweet Grass County: 21.3 %Teton County: 23.3 %Toole County: 18.7 %Treasure County: 19 %Valley County: 22.4 %Wheatland County: 22.1 %Wibaux County: 23.2 %Yellowstone County: 23.7 %
  • Under 18
  • 18 to 20
  • 20 to 21
  • 21 to 22
  • 22 to 24
  • 24 and over
%, 2017. Source: Invokely calculation with data from U.S. Census Bureau. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2017

Big Horn County: 34.2 %Big Horn County34.2Roosevelt County: 31.8 %Roosevelt County31.8Glacier County: 31.2 %Glacier County31.2Blaine County: 29.5 %Blaine County29.5Rosebud County: 27.8 %Rosebud County27.8Fallon County: 27.2 %Fallon County27.2Hill County: 26.7 %Hill County26.7Chouteau County: 25.7 %Chouteau County25.7Pondera County: 24.6 %Pondera County24.6Richland County: 24.5 %Richland County24.5Lake County: 24.1 %Lake County24.1Garfield County: 24.1 %Garfield County24.1Phillips County: 23.7 %Phillips County23.7Liberty County: 23.7 %Liberty County23.7Yellowstone County: 23.7 %Yellowstone County23.7Teton County: 23.3 %Teton County23.3Wibaux County: 23.2 %Wibaux County23.2Custer County: 22.8 %Custer County22.8Dawson County: 22.5 %Dawson County22.5Valley County: 22.4 %Valley County22.4Cascade County: 22.4 %Cascade County22.4Flathead County: 22.3 %Flathead County22.3Wheatland County: 22.1 %Wheatland County22.1Daniels County: 21.7 %Daniels County21.7Lewis and Clark County: 21.6 %Lewis and Clark County21.6Broadwater County: 21.6 %Broadwater County21.6Carter County: 21.4 %Carter County21.4Sweet Grass County: 21.3 %Sweet Grass County21.3Stillwater County: 21.1 %Stillwater County21.1McCone County: 21.1 %McCone County21.1Jefferson County: 20.9 %Jefferson County20.9Fergus County: 20.9 %Fergus County20.9Sheridan County: 20.5 %Sheridan County20.5Golden Valley County: 20.4 %Golden Valley County20.4Gallatin County: 20.3 %Gallatin County20.3Silver Bow County: 20 %Silver Bow County20Ravalli County: 20 %Ravalli County20Missoula County: 19.9 %Missoula County19.9Musselshell County: 19.6 %Musselshell County19.6Beaverhead County: 19.5 %Beaverhead County19.5Petroleum County: 19.3 %Petroleum County19.3Treasure County: 19 %Treasure County19Carbon County: 19 %Carbon County19Powder River County: 18.8 %Powder River County18.8Toole County: 18.7 %Toole County18.7Lincoln County: 18.6 %Lincoln County18.6Mineral County: 18.5 %Mineral County18.5Granite County: 18.4 %Granite County18.4Judith Basin County: 18.2 %Judith Basin County18.2Sanders County: 18.2 %Sanders County18.2Park County: 18.1 %Park County18.1Prairie County: 17.7 %Prairie County17.7Deer Lodge County: 17 %Deer Lodge County17Meagher County: 17 %Meagher County17Madison County: 16.2 %Madison County16.2Powell County: 14.7 %Powell County14.7Big Horn County: 34.2 %Big Horn County34.2Roosevelt County: 31.8 %Roosevelt County31.8Glacier County: 31.2 %Glacier County31.2Blaine County: 29.5 %Blaine County29.5Rosebud County: 27.8 %Rosebud County27.8Fallon County: 27.2 %Fallon County27.2Hill County: 26.7 %Hill County26.7Chouteau County: 25.7 %Chouteau County25.7Pondera County: 24.6 %Pondera County24.6Richland County: 24.5 %Richland County24.5Lake County: 24.1 %Lake County24.1Garfield County: 24.1 %Garfield County24.1Phillips County: 23.7 %Phillips County23.7Liberty County: 23.7 %Liberty County23.7Yellowstone County: 23.7 %Yellowstone County23.7Teton County: 23.3 %Teton County23.3Wibaux County: 23.2 %Wibaux County23.2Custer County: 22.8 %Custer County22.8Dawson County: 22.5 %Dawson County22.5Valley County: 22.4 %Valley County22.4Cascade County: 22.4 %Cascade County22.4Flathead County: 22.3 %Flathead County22.3Wheatland County: 22.1 %Wheatland County22.1Daniels County: 21.7 %Daniels County21.7Lewis and Clark County: 21.6 %Lewis and Clark County21.6Broadwater County: 21.6 %Broadwater County21.6Carter County: 21.4 %Carter County21.4Sweet Grass County: 21.3 %Sweet Grass County21.3Stillwater County: 21.1 %Stillwater County21.1McCone County: 21.1 %McCone County21.1Jefferson County: 20.9 %Jefferson County20.9Fergus County: 20.9 %Fergus County20.9Sheridan County: 20.5 %Sheridan County20.5Golden Valley County: 20.4 %Golden Valley County20.4Gallatin County: 20.3 %Gallatin County20.3Silver Bow County: 20 %Silver Bow County20Ravalli County: 20 %Ravalli County20Missoula County: 19.9 %Missoula County19.9Musselshell County: 19.6 %Musselshell County19.6Beaverhead County: 19.5 %Beaverhead County19.5Petroleum County: 19.3 %Petroleum County19.3Treasure County: 19 %Treasure County19Carbon County: 19 %Carbon County19Powder River County: 18.8 %Powder River County18.8Toole County: 18.7 %Toole County18.7Lincoln County: 18.6 %Lincoln County18.6Mineral County: 18.5 %Mineral County18.5Granite County: 18.4 %Granite County18.4Judith Basin County: 18.2 %Judith Basin County18.2Sanders County: 18.2 %Sanders County18.2Park County: 18.1 %Park County18.1Prairie County: 17.7 %Prairie County17.7Deer Lodge County: 17 %Deer Lodge County17Meagher County: 17 %Meagher County17Madison County: 16.2 %Madison County16.2Powell County: 14.7 %Powell County14.7
%. Source: Invokely calculation with data from U.S. Census Bureau. Retrieved 2026-10-12.

Full ranking

RankCounties2017 (%)Change on 2016
1Big Horn County34.2+0.5 pts
2Roosevelt County31.8+0.1 pts
3Glacier County31.20 pts
4Blaine County29.5+0.2 pts
5Rosebud County27.8-0.4 pts
6Fallon County27.2+0.3 pts
7Hill County26.7+0.1 pts
8Chouteau County25.7-0 pts
9Pondera County24.6+0.3 pts
10Richland County24.5-0.6 pts
11Lake County24.1-0.3 pts
12Garfield County24.1+0.8 pts
13Phillips County23.7+0.3 pts
14Liberty County23.7-0.4 pts
15Yellowstone County23.70 pts
16Teton County23.3+0.2 pts
17Wibaux County23.2-0.4 pts
18Custer County22.80 pts
19Dawson County22.5-0.5 pts
20Valley County22.4-0.5 pts
21Cascade County22.4+0.1 pts
22Flathead County22.3-0.1 pts
23Wheatland County22.1+0.8 pts
24Daniels County21.7-0.2 pts
25Lewis and Clark County21.6-0.1 pts
26Broadwater County21.6-0 pts
27Carter County21.4+1.6 pts
28Sweet Grass County21.3-0.3 pts
29Stillwater County21.1+0.1 pts
30McCone County21.1+0.6 pts
31Jefferson County20.9+0.1 pts
32Fergus County20.9-0.3 pts
33Sheridan County20.5-0.8 pts
34Golden Valley County20.4-0.2 pts
35Gallatin County20.3-0.2 pts
36Silver Bow County20-0.2 pts
37Ravalli County20-0.1 pts
38Missoula County19.9-0.1 pts
39Musselshell County19.6-0.3 pts
40Beaverhead County19.5+0.1 pts
41Petroleum County19.3-0 pts
42Treasure County19-0 pts
43Carbon County19+0.3 pts
44Powder River County18.8-0 pts
45Toole County18.7+0.5 pts
46Lincoln County18.6-0 pts
47Mineral County18.5+0.7 pts
48Granite County18.4-0.4 pts
49Judith Basin County18.2+0.5 pts
50Sanders County18.2-0.2 pts
51Park County18.1-0.5 pts
52Prairie County17.7-1.5 pts
53Deer Lodge County17+0.1 pts
54Meagher County17+0.5 pts
55Madison County16.2+0.1 pts
56Powell County14.7-0.8 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, 2017) [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, 2017. 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=2017. 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, 2017. 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=2017.

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, 2017 [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=2017 (Accessed: 12 October 2026).

BibTeX
@misc{census_counties_in_montana_by_2017,
  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, 2017}},
  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=2017. 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, 2017
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=2017
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/population-under-18/montana-counties?period=2017.
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  -
Embed this chart

Paste this code into a web page or a blog post. The chart shows the latest figures as they are published, with the source and a link back to this page.

Sites that read oEmbed links, such as WordPress, can show the chart when you paste the link to this page.

Use this data in your AI agent

Invokely serves this figure to AI assistants through MCP and to code through a REST API, with the source and citation attached. Ask your assistant:

Rank Counties in Montana by population under 18 using official data, and cite the source.
rank_places {"indicator":"population_0_17_share","level":"province","within":"Montana","limit":10}
GET https://invokely.ai/api/v1/rank?indicator=population_0_17_share&level=province&within=Montana&limit=10

Connect Claude, ChatGPT or Cursor in one step. The trial answers 25 calls a day without an account.

Questions

Which county has the highest population under 18?

Big Horn County, with 34.2% in 2017, according to the U.S. Census Bureau.

Which county has the lowest population under 18?

Powell County, with 14.7% in 2017.

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