| Name | Jefferson County |
| State | Montana |
| FIPS Code | 30043 |
| County Seat | Boulder |
| Timezone | Mountain Daylight Time (MDT) |
| Population (2024) | 13,086 |
| Population Growth Rate(2020-2024) | 7.67% |
| Majority Ethnicity | White 95.32% |
| Public School Majority Ethnicity | White 90% |
| Partisan Voting Index | Republican:+18 |
| Unemployment Rate (May 2026) | 3.6% |
| Sales Tax Rate (2025) | 0% |
| Area Code(s) | 406 |
| Race/Ethnicity | Percentage of Population (2023) |
|---|---|
| White | 95.32% |
| African American | 0.12% |
| Hispanic | 2.79% |
| Asian | 0.42% |
| Native American | 1.36% |
| Hawaiin/Pacific Islander | 0% |
| Race/Ethnicity | Percentage of Public School Students (2023) |
|---|---|
| White | 90.4% |
| African American | 0.27% |
| Hispanic | 4.46% |
| Asian | 0.27% |
| Native American | 1.38% |
| Hawaiin/Pacific Islander | 0.11% |