# Counties in Montana by median age on 1 July (US county estimates), 2025

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

- Indicator id: `median_age_pep`
- Unit: years
- Definition: Age that divides the resident population of a US county into two halves of equal size on 1 July, from Census Bureau population estimates calculated by single year of age.
- Source: U.S. Census Bureau, Population Estimates Program, county population by age and sex: median age (MEDIAN_AGE_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage (https://www.census.gov/programs-surveys/popest/data/data-sets.html)
- Publisher page: https://invokely.ai/en/publishers/us-census-bureau
- Retrieved: 2026-10-12
- Citation: U.S. Census Bureau. Population Estimates Program, county population by age and sex: median age (MEDIAN_AGE_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage. https://www.census.gov/programs-surveys/popest/data/data-sets.html. Retrieved 2026-10-12.
- Web page: https://invokely.ai/rankings/median-age-july-1-us-counties/montana-counties

| Rank | Place | years |
|---:|---|---:|
| 1 | Petroleum County | 56.7 |
| 2 | Sanders County | 54.9 |
| 3 | Prairie County | 54.6 |
| 4 | Lincoln County | 52.4 |
| 5 | Granite County | 51.5 |
| 6 | Mineral County | 51.3 |
| 7 | Deer Lodge County | 51.1 |
| 8 | Judith Basin County | 50.9 |
| 9 | Carbon County | 50.5 |
| 10 | Meagher County | 50.4 |
| 11 | Sweet Grass County | 49.9 |
| 12 | Madison County | 49.7 |
| 13 | Golden Valley County | 49.5 |
| 13 | Powder River County | 49.5 |
| 15 | Ravalli County | 49.2 |
| 16 | Stillwater County | 48.1 |
| 17 | Musselshell County | 48 |
| 18 | Wheatland County | 47.5 |
| 19 | McCone County | 47.3 |
| 20 | Jefferson County | 47.2 |
| 21 | Wibaux County | 46.4 |
| 22 | Sheridan County | 46.3 |
| 23 | Park County | 46 |
| 23 | Treasure County | 46 |
| 25 | Daniels County | 45.7 |
| 25 | Fergus County | 45.7 |
| 25 | Powell County | 45.7 |
| 28 | Lake County | 45.3 |
| 29 | Carter County | 44.7 |
| 29 | Valley County | 44.7 |
| 31 | Phillips County | 44.3 |
| 32 | Chouteau County | 44.2 |
| 32 | Garfield County | 44.2 |
| 34 | Broadwater County | 43.7 |
| 35 | Teton County | 43.5 |
| 36 | Beaverhead County | 43.3 |
| 37 | Flathead County | 42.5 |
| 38 | Lewis and Clark County | 42.4 |
| 39 | Pondera County | 42.2 |
| 40 | Liberty County | 42.1 |
| 41 | Custer County | 42 |
| 41 | Dawson County | 42 |
| 43 | Silver Bow County | 41.9 |
| 44 | Fallon County | 40.8 |
| 45 | Yellowstone County | 39.7 |
| 46 | Richland County | 39.6 |
| 47 | Toole County | 39.3 |
| 48 | Cascade County | 39.1 |
| 49 | Missoula County | 38.8 |
| 50 | Rosebud County | 37.5 |
| 51 | Blaine County | 36.7 |
| 52 | Hill County | 35.8 |
| 53 | Glacier County | 34.9 |
| 54 | Gallatin County | 34.8 |
| 55 | Roosevelt County | 32.9 |
| 56 | Big Horn County | 32.8 |