Jefferson County's 2026 population is estimated at 13,740, reflecting a 1.61% growth rate over the past year (World Population Review estimate based on U.S. Census Bureau data). Jefferson County is the 14th largest county in Montana. The 2010 population was 11,406 and has grown 20.46% since 2010.
Data after 2023 is projected based on recent change
Overall: 47.1 years
Female: 47 years
Male: 47.1 years
There are 10,219 adults, (2,961 of whom are seniors) in Jefferson County.
Female: 6,315 (49.4%)
Male: 6,459 (50.6%)
The racial composition of Jefferson County includes 91.73% White, and smaller percentages for Native American, other race, Asian, Black or African American and multiracial populations.
| Race | Population ↓ | Percentage (of total) |
|---|---|---|
| White | 11,717 | 91.73% |
| Two or more races | 698 | 5.46% |
| Native American | 188 | 1.47% |
| Other race | 117 | 0.92% |
| Asian | 50 | 0.39% |
| Black or African American | 4 | 0.03% |
Jefferson County 's average per capita income is $51,669. Household income levels show a median of $95,490. The poverty rate stands at 5.72%.
| Name | Median ↓ | Mean |
|---|---|---|
| Married Families | $122,754 | - |
| Families | $109,206 | $140,331 |
| Households | $95,490 | $123,428 |
| Non Families | $55,125 | $71,543 |
Average Income
Median Household Income
Poverty Rate
