# Counties in Montana by population aged 18 to 64, 2025

All 56 values come from U.S. Census Bureau for 2025, so the places are comparable.

- Indicator id: `population_18_64_share`
- Unit: %
- Definition: 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.
- Source: 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: 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.
- Web page: https://invokely.ai/rankings/population-18-64/montana-counties

| Rank | Place | % |
|---:|---|---:|
| 1 | Gallatin County | 67.4 |
| 2 | Missoula County | 62.8 |
| 3 | Toole County | 60.5 |
| 4 | Powell County | 59.4 |
| 5 | Silver Bow County | 58.4 |
| 6 | Yellowstone County | 58.1 |
| 7 | Park County | 58 |
| 8 | Beaverhead County | 57.7 |
| 9 | Cascade County | 57.6 |
| 10 | Lewis and Clark County | 57.6 |
| 11 | Richland County | 57 |
| 12 | Custer County | 56.4 |
| 13 | Glacier County | 56 |
| 14 | Flathead County | 55.7 |
| 15 | Dawson County | 55.6 |
| 16 | Deer Lodge County | 55.5 |
| 17 | Broadwater County | 55.4 |
| 18 | Big Horn County | 54.5 |
| 19 | Granite County | 54.3 |
| 20 | Blaine County | 54.3 |
| 21 | Hill County | 54.3 |
| 22 | Madison County | 53.7 |
| 23 | Sheridan County | 53.5 |
| 24 | Chouteau County | 53.4 |
| 25 | Jefferson County | 53.4 |
| 26 | Rosebud County | 53.4 |
| 27 | Mineral County | 53.3 |
| 28 | Roosevelt County | 53.2 |
| 29 | Wibaux County | 52.9 |
| 30 | Valley County | 52.3 |
| 31 | Fallon County | 52.3 |
| 32 | Pondera County | 52.2 |
| 33 | Musselshell County | 52.1 |
| 34 | Lake County | 52 |
| 35 | Sweet Grass County | 51.8 |
| 36 | Ravalli County | 51.5 |
| 37 | Carbon County | 51.4 |
| 38 | Phillips County | 51.2 |
| 39 | Stillwater County | 51.1 |
| 40 | Liberty County | 51 |
| 41 | McCone County | 51 |
| 42 | Teton County | 50.6 |
| 43 | Fergus County | 50.6 |
| 44 | Meagher County | 50.5 |
| 45 | Wheatland County | 50.4 |
| 46 | Daniels County | 50 |
| 47 | Lincoln County | 49.9 |
| 48 | Carter County | 49.7 |
| 49 | Garfield County | 49.1 |
| 50 | Judith Basin County | 49.1 |
| 51 | Powder River County | 49.1 |
| 52 | Sanders County | 48.7 |
| 53 | Petroleum County | 48.5 |
| 54 | Golden Valley County | 47.9 |
| 55 | Treasure County | 46.4 |
| 56 | Prairie County | 41.2 |