Data / Rankings / Population aged 18 to 64 / Counties in Montana

Counties in Montana by population aged 18 to 64

Gallatin County had the highest population aged 18 to 64 of 56 counties in 2018, at 67.2%. Golden Valley County had the lowest, at 50.9%. The median was 55.1% and the figure for Montana was 59.3%. Source: the U.S. Census Bureau.

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Highest67.2Gallatin County
Lowest50.9Golden Valley County
Median55.156 counties
Montana59.3History

Map of counties, 2018

Beaverhead County: 57.8 %Big Horn County: 53.7 %Blaine County: 55.7 %Broadwater County: 55.9 %Carbon County: 56.5 %Carter County: 52.5 %Cascade County: 59.4 %Chouteau County: 53.9 %Custer County: 57.6 %Daniels County: 53.1 %Dawson County: 58.2 %Deer Lodge County: 58.9 %Fallon County: 56.8 %Fergus County: 54 %Flathead County: 57.8 %Gallatin County: 67.2 %Garfield County: 51.9 %Glacier County: 56.8 %Golden Valley County: 50.9 %Granite County: 53.5 %Hill County: 57.9 %Jefferson County: 56.6 %Judith Basin County: 54.4 %Lake County: 53.6 %Lewis and Clark County: 59.9 %Liberty County: 55.3 %Lincoln County: 52.9 %McCone County: 55.3 %Madison County: 54.8 %Meagher County: 52.7 %Mineral County: 54.6 %Missoula County: 64.1 %Musselshell County: 54.8 %Park County: 60.4 %Petroleum County: 53.3 %Phillips County: 54.3 %Pondera County: 54.3 %Powder River County: 54.5 %Powell County: 64.3 %Prairie County: 52.1 %Ravalli County: 53.8 %Richland County: 60.5 %Roosevelt County: 55.5 %Rosebud County: 56.3 %Sanders County: 51.2 %Sheridan County: 56.1 %Silver Bow County: 60.1 %Stillwater County: 55.9 %Sweet Grass County: 53.6 %Teton County: 53.1 %Toole County: 63.2 %Treasure County: 51.8 %Valley County: 54.8 %Wheatland County: 53.3 %Wibaux County: 53.4 %Yellowstone County: 59.5 %
  • Under 53
  • 53 to 54
  • 54 to 55
  • 55 to 57
  • 57 to 59
  • 59 and over
%, 2018. Source: Invokely calculation with data from U.S. Census Bureau. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2018

Gallatin County: 67.2 %Gallatin County67.2Powell County: 64.3 %Powell County64.3Missoula County: 64.1 %Missoula County64.1Toole County: 63.2 %Toole County63.2Richland County: 60.5 %Richland County60.5Park County: 60.4 %Park County60.4Silver Bow County: 60.1 %Silver Bow County60.1Lewis and Clark County: 59.9 %Lewis and Clark County59.9Yellowstone County: 59.5 %Yellowstone County59.5Cascade County: 59.4 %Cascade County59.4Deer Lodge County: 58.9 %Deer Lodge County58.9Dawson County: 58.2 %Dawson County58.2Hill County: 57.9 %Hill County57.9Beaverhead County: 57.8 %Beaverhead County57.8Flathead County: 57.8 %Flathead County57.8Custer County: 57.6 %Custer County57.6Glacier County: 56.8 %Glacier County56.8Fallon County: 56.8 %Fallon County56.8Jefferson County: 56.6 %Jefferson County56.6Carbon County: 56.5 %Carbon County56.5Rosebud County: 56.3 %Rosebud County56.3Sheridan County: 56.1 %Sheridan County56.1Stillwater County: 55.9 %Stillwater County55.9Broadwater County: 55.9 %Broadwater County55.9Blaine County: 55.7 %Blaine County55.7Roosevelt County: 55.5 %Roosevelt County55.5Liberty County: 55.3 %Liberty County55.3McCone County: 55.3 %McCone County55.3Valley County: 54.8 %Valley County54.8Madison County: 54.8 %Madison County54.8Musselshell County: 54.8 %Musselshell County54.8Mineral County: 54.6 %Mineral County54.6Powder River County: 54.5 %Powder River County54.5Judith Basin County: 54.4 %Judith Basin County54.4Pondera County: 54.3 %Pondera County54.3Phillips County: 54.3 %Phillips County54.3Fergus County: 54 %Fergus County54Chouteau County: 53.9 %Chouteau County53.9Ravalli County: 53.8 %Ravalli County53.8Big Horn County: 53.7 %Big Horn County53.7Sweet Grass County: 53.6 %Sweet Grass County53.6Lake County: 53.6 %Lake County53.6Granite County: 53.5 %Granite County53.5Wibaux County: 53.4 %Wibaux County53.4Petroleum County: 53.3 %Petroleum County53.3Wheatland County: 53.3 %Wheatland County53.3Teton County: 53.1 %Teton County53.1Daniels County: 53.1 %Daniels County53.1Lincoln County: 52.9 %Lincoln County52.9Meagher County: 52.7 %Meagher County52.7Carter County: 52.5 %Carter County52.5Prairie County: 52.1 %Prairie County52.1Garfield County: 51.9 %Garfield County51.9Treasure County: 51.8 %Treasure County51.8Sanders County: 51.2 %Sanders County51.2Golden Valley County: 50.9 %Golden Valley County50.9Gallatin County: 67.2 %Gallatin County67.2Powell County: 64.3 %Powell County64.3Missoula County: 64.1 %Missoula County64.1Toole County: 63.2 %Toole County63.2Richland County: 60.5 %Richland County60.5Park County: 60.4 %Park County60.4Silver Bow County: 60.1 %Silver Bow County60.1Lewis and Clark County: 59.9 %Lewis and Clark County59.9Yellowstone County: 59.5 %Yellowstone County59.5Cascade County: 59.4 %Cascade County59.4Deer Lodge County: 58.9 %Deer Lodge County58.9Dawson County: 58.2 %Dawson County58.2Hill County: 57.9 %Hill County57.9Beaverhead County: 57.8 %Beaverhead County57.8Flathead County: 57.8 %Flathead County57.8Custer County: 57.6 %Custer County57.6Glacier County: 56.8 %Glacier County56.8Fallon County: 56.8 %Fallon County56.8Jefferson County: 56.6 %Jefferson County56.6Carbon County: 56.5 %Carbon County56.5Rosebud County: 56.3 %Rosebud County56.3Sheridan County: 56.1 %Sheridan County56.1Stillwater County: 55.9 %Stillwater County55.9Broadwater County: 55.9 %Broadwater County55.9Blaine County: 55.7 %Blaine County55.7Roosevelt County: 55.5 %Roosevelt County55.5Liberty County: 55.3 %Liberty County55.3McCone County: 55.3 %McCone County55.3Valley County: 54.8 %Valley County54.8Madison County: 54.8 %Madison County54.8Musselshell County: 54.8 %Musselshell County54.8Mineral County: 54.6 %Mineral County54.6Powder River County: 54.5 %Powder River County54.5Judith Basin County: 54.4 %Judith Basin County54.4Pondera County: 54.3 %Pondera County54.3Phillips County: 54.3 %Phillips County54.3Fergus County: 54 %Fergus County54Chouteau County: 53.9 %Chouteau County53.9Ravalli County: 53.8 %Ravalli County53.8Big Horn County: 53.7 %Big Horn County53.7Sweet Grass County: 53.6 %Sweet Grass County53.6Lake County: 53.6 %Lake County53.6Granite County: 53.5 %Granite County53.5Wibaux County: 53.4 %Wibaux County53.4Petroleum County: 53.3 %Petroleum County53.3Wheatland County: 53.3 %Wheatland County53.3Teton County: 53.1 %Teton County53.1Daniels County: 53.1 %Daniels County53.1Lincoln County: 52.9 %Lincoln County52.9Meagher County: 52.7 %Meagher County52.7Carter County: 52.5 %Carter County52.5Prairie County: 52.1 %Prairie County52.1Garfield County: 51.9 %Garfield County51.9Treasure County: 51.8 %Treasure County51.8Sanders County: 51.2 %Sanders County51.2Golden Valley County: 50.9 %Golden Valley County50.9
%. Source: Invokely calculation with data from U.S. Census Bureau. Retrieved 2026-10-12.

Full ranking

RankCounties2018 (%)Change on 2017
1Gallatin County67.2-0.4 pts
2Powell County64.3-0.2 pts
3Missoula County64.1-0.5 pts
4Toole County63.2-1.1 pts
5Richland County60.5-0.5 pts
6Park County60.4-0.2 pts
7Silver Bow County60.1-0.7 pts
8Lewis and Clark County59.9-0.5 pts
9Yellowstone County59.5-0.3 pts
10Cascade County59.4-0.2 pts
11Deer Lodge County58.9-1.1 pts
12Dawson County58.2-0.5 pts
13Hill County57.9-0.1 pts
14Beaverhead County57.8-0.9 pts
15Flathead County57.8-0.5 pts
16Custer County57.6-0.2 pts
17Glacier County56.8-0.3 pts
18Fallon County56.8-0.1 pts
19Jefferson County56.6-0.9 pts
20Carbon County56.5-0.1 pts
21Rosebud County56.3-0.3 pts
22Sheridan County56.1-1.3 pts
23Stillwater County55.9-0.9 pts
24Broadwater County55.9-0.3 pts
25Blaine County55.7+0.1 pts
26Roosevelt County55.5-0.4 pts
27Liberty County55.3-0.8 pts
28McCone County55.3-0.7 pts
29Valley County54.8-0.6 pts
30Madison County54.8-1 pts
31Musselshell County54.8-1.1 pts
32Mineral County54.60 pts
33Powder River County54.5-2.5 pts
34Judith Basin County54.4-1.6 pts
35Pondera County54.3-0.5 pts
36Phillips County54.3-0.7 pts
37Fergus County54-0.7 pts
38Chouteau County53.9-1.3 pts
39Ravalli County53.8-0.7 pts
40Big Horn County53.7-0.1 pts
41Sweet Grass County53.6-0.7 pts
42Lake County53.6-0.4 pts
43Granite County53.5-0.8 pts
44Wibaux County53.4+0.9 pts
45Petroleum County53.3-1.3 pts
46Wheatland County53.3+0.6 pts
47Teton County53.1-0.6 pts
48Daniels County53.1-0.1 pts
49Lincoln County52.9-0.8 pts
50Meagher County52.7-2.2 pts
51Carter County52.5-1.4 pts
52Prairie County52.1-0.4 pts
53Garfield County51.9+0.4 pts
54Treasure County51.8-2.3 pts
55Sanders County51.2-0.9 pts
56Golden Valley County50.9-1.9 pts

Other periods

About this ranking

Residents aged 18 to 64 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.

Not comparable with working-age shares for ages 15 to 64 used in EU and World Bank statistics.

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 18 to 64 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 18 to 64 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 aged 18 to 64, 2018) [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 18 to 64 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 aged 18 to 64, 2018. U.S. Census Bureau, 25 June 2026, https://www.census.gov/programs-surveys/popest/data/data-sets.html. Invokely, https://invokely.ai/rankings/population-18-64/montana-counties?period=2018. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Census Bureau. 2026. Population Estimates Program, county population by age and sex: residents aged 18 to 64 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 aged 18 to 64, 2018. 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-18-64/montana-counties?period=2018.

Harvard

U.S. Census Bureau (2026) Population Estimates Program, county population by age and sex: residents aged 18 to 64 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 aged 18 to 64, 2018 [Dataset]. Available at: https://www.census.gov/programs-surveys/popest/data/data-sets.html, via Invokely: https://invokely.ai/rankings/population-18-64/montana-counties?period=2018 (Accessed: 12 October 2026).

BibTeX
@misc{census_counties_in_montana_by_2018,
  author = {{U.S. Census Bureau}},
  title = {{Population Estimates Program, county population by age and sex: residents aged 18 to 64 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 aged 18 to 64, 2018}},
  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-18-64/montana-counties?period=2018. Publisher attribution: U.S. Census Bureau. Population Estimates Program, county population by age and sex: residents aged 18 to 64 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 18 to 64 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 aged 18 to 64, 2018
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-18-64/montana-counties?period=2018
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/population-18-64/montana-counties?period=2018.
N1  - Publisher attribution: U.S. Census Bureau. Population Estimates Program, county population by age and sex: residents aged 18 to 64 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 aged 18 to 64?

Gallatin County, with 67.2% in 2018, according to the U.S. Census Bureau.

Which county has the lowest population aged 18 to 64?

Golden Valley County, with 50.9% in 2018.

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 18 to 64 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 aged 18 to 64: other rankings

Counties in Montana: more rankings